Measurement of the neutron lifetime with ultra-cold neutrons stored

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Measurement of the neutron lifetime with ultra-cold neutrons stored
in a magneto-gravitational trap
V.F. Ezhov,1,5 A.Z. Andreev,1 G. Ban,2 B.A. Bazarov,1 P. Geltenbort,3 A.G. Glushkov,1
V.A. Knyazkov,1 N.A. Kovrizhnykh,4 G.B. Krygin,1 O. Naviliat-Cuncic,2,* and V.L. Ryabov1
2LPC
1Petersburg
Nuclear Physics Institute NRS KI, Gatchina, Russia
Caen, ENSICAEN, Université de Caen Basse-Normandie, CNRS/IN2P3, Caen, France
3Institut Laue-Langevin, Grenoble, France
4Institute of Electro-Physical Apparatuses, Gatchina, Russia
5Saint-Petersburg State University, Saint-Petersburg, Russia
(Dated: December 23, 2014)
We report a new measurement of the neutron lifetime using ultra-cold neutrons stored
in a magneto-gravitational trap made of permanent magnets. Neutrons surviving in the trap
after fixed storage times have been counted and the trap losses have continuously been monitored during storage by detecting neutrons leaking from the trap. The value of the neutron
lifetime resulting from this measurement is n = (878.3±1.9) s. It is the most precise measurement of the neutron lifetime obtained with magnetically stored neutrons.
PACS numbers: 23.40.-s; 23.40.Bw; 24.80.+y
Precision measurements of the neutron lifetime provide stringent tests of the standard electroweak model
[1] as well as crucial inputs for Big-Bang nucleosynthesis (BBN) calculations [2]. When combined with
measurements of other neutron beta decay correlation coefficients [1], the neutron lifetime enables the
determination of the Vud element of the Cabbibo-Kobayashi-Maskawa quark mixing matrix, providing a complementary unitarity test to that obtained from superallowed nuclear beta decay [3]. The neutron lifetime is
also one of the key parameters for the determination
of yields of light elements in BBN since the ratio between the free neutron and proton abundances drives
the extent of fusion reactions during the first few
minutes of the Universe [2].
The present world average value of the neutron lifetime as quoted by the Particle Data Group (PDG),
n = (880.3±1.1) s [4], is dominated by results obtained using ultra-cold neutrons (UCN) in material
bottles. These results, and in particular the most precise of them [5], appear to be systematically lower
than results obtained using a neutron beam and
counting trapped protons following neutron decay [6].
A detailed discussion of the experimental methods
and results can be found in Ref. [7].
The large discrepancy between the results indicates
that all systematic effects are not fully under control.
The importance of the neutron lifetime in particle
physics and cosmology calls for alternative measuring
techniques, with high sensitivity but other potential
sources of systematic effects. We report here a new
measurement of the neutron lifetime using UCN
stored in a magneto-gravitational trap made of permanent magnets.
The repulsive force resulting from the interaction
between the neutron magnetic moment and a magnetic field gradient can be used for the confinement of
neutrons provided their energies are sufficiently low
[8]. This has been incorporated for the measurement
of the neutron lifetime in various configurations, the
most successful having been a sextupole storage ring [9],
leading to n = (877±10) s, an Ioffe-Pritchard three dimensional trap leading to a storage time S = (833+74
−63 ) s
[10], and an asymmetric Halbach array trap, with a storage
time S = (860±19) s [11].
The experimental setup used in the present measurement (Fig. 1) was operated at one of the beam positions of the UCN source PF2 at the Institut Laue-Langevin (ILL) in Grenoble. It comprises five main parts: a
lift to fill the trap; the magnetic trap; a solenoidal magnet with a yoke; an outer coil around the magnetic
trap; and the UCN detector. The central element of the
setup is the magneto-gravitational trap made of NdFeB
permanent magnets sandwiched between FeCo poles to
generate twenty-poles. The trap is a vertical cylinder
open at the top with a conical lower part open at the
bottom. The central magnetic field generated by the
poles is horizontal and the field gradient near the magnet surfaces is about 2 T/cm when moving toward the
vertical axis of the trap. The trap is wrapped with an external coil to eliminate zero field regions in the trap volume. The magnets surfaces were covered with Fomblin
grease (UT18 type) in order to reflect those neutrons
which are not repelled by the magnetic field gradient
and hit the magnet surfaces. Other technical details
about the trap properties and design have been reported elsewhere [12,13].
A crucial aspect for the storage of UCN in magnetic
traps is the filling of the trap. In previous experiments
1
J. Nucl. Med., Vol. 0, No. 0, pp. 1–21 (2014)
arXiv:1412.7389v1 [physics.med-ph] 23 Dec 2014
Towards a Radio-guided Surgery with β − Decays: Uptake
of a somatostatin analogue (DOTATOC) in Meningioma and
High Grade Glioma.
Francesco Collamati1,2 , Alessandra Pepe3 , Fabio Bellini1,2 , Valerio Bocci2 , Marta Cremonesi 4 , Erika De Lucia5 , Mahila Ferrari4 , Paola M. Frallicciardi2,6 , Chiara M.
Grana4 , Michela Marafini2,6 , Ilaria Mattei5,7 , Silvio Morganti2 , Vincenzo Patera2,3 ,
Luca Piersanti2,3 , Luigi Recchia2 , Andrea Russomando1,2,8 , Alessio Sarti5,3 , Adalberto Sciubba2,3 , Martina Senzacqua1,2 , Elena Solfaroli Camillocci8 , Cecilia Voena2 ,
Riccardo Faccini1,2
1
Dipartimento di Fisica, Sapienza Università di Roma, Roma, Italy; 2 INFN Sezione
di Roma, Roma, Italy; 3 Dipartimento di Scienze di Base e Applicate per l’Ingegneria,
Sapienza Università di Roma, Roma, Italy; 4 Istituto Europeo di Oncologia, Milano, Italy; 5 Laboratori Nazionali di Frascati dell’INFN, Frascati, Italy; 6 Museo
Storico della Fisica e Centro Studi e Ricerche “E. Fermi”, Roma, Italy; 7 Dipartimento di Fisica, Università RomaTre, Roma, Italy; 8 Center for Life Nano [email protected], Istituto Italiano di Tecnologia, Roma, Italy.
24th December 2014
Corresponding author : R. Faccini, Dip. Fisica, Universita’ di Roma "La Sapienza", P.le A. Moro 2, 00185, Rome, Italy. email: [email protected],
tel: +39 0649914798, fax: +39 06 4957697.
First author : F. Collamati, Ph.D. student, Dip. Fisica, Universita’ di Roma "La
Sapienza", P.le A. Moro 2, 00185, Rome, Italy. email: [email protected],
tel: +39 0649914998, fex: +39 06 4957697
Word Count: 3600 words
The study was financed by the research funds of the Università di Roma "La
Sapienza"
Short Running Title: DOTATOC Uptake In Meningioma and Glioma
Towards a Radio-guided Surgery with β − Decays: Uptake of a somatostatin analogue (DOTATOC)
in Meningioma and High Grade Glioma.
2
Abstract
A novel radio guided surgery (RGS) technique for cerebral tumors using β − radiation is being developed. Checking the availability of a radio-tracer that can
deliver a β − emitter to the tumor is a fundamental step in the deployment of
such technique. This paper reports a study of the uptake of 90 Y-labeled [1,4,7,10tetraazacyclododecane-N,N0 ,N00 ,N000 -tetraacetic acid0-D-Phe1,Tyr3]octreotide (DOTATOC) in the meningioma and the high grade glioma (HGG) and a feasibility study
of the RGS technique in these cases. Such estimates are performed assuming the use
of a β − probe with a sensitive area of 2.55 mm radius, that is under development, to
detect 0.1ml residuals. Methods: the uptake and the background from healthy tissues were estimated on 68 Ga-DOTATOC PET scans of 11 meningioma and 12 HGG
patients. A dedicated statistical analysis of the DICOM images was developed and
validated. The feasibility study was performed by means of a full simulation of the
emission and detection of the radiation, accounting for the measured uptake and
background rate. Results: all meningioma patients but one with an atypical extracranial tumor showed a very high uptake of DOTATOC. In terms of feasibility of
the RGS technique, we estimated that by administering 3 MBq/kg of radio-tracer,
the time needed to detect a 0.1 ml remnant at 95% C.L. is smaller than 1 s. Actually,
to achieve a detection time of 1 s the required activities to administer are as low
as 0.2-0.5 MBq/kg in a large fraction of the patients. In case of HGGs, the uptake
is lower, but the tumor-to-non-tumor ratio is higher than four, which implies that
it can still be effective for RGS. It was estimated that by administering 3 MBq of
radio-tracer, the time needed to detect a 0.1 ml remnant at 95% C.L. is smaller than
6 s with the exception of the only oligodendrioma in the sample. Conclusion: The
uptake of 90 Y-DOTATOC in meningioma is high in all studied patients. As far as
HGG is concerned, albeit the uptake is significantly worse, it is still acceptable for
RGS, in particular if further R&D is made to improve the performances of the β −
probe.
Keywords:Radio Guided Surgery, somatostatin analogue, Meningioma, High
Grade Glioma.
Photoacoustics meets ultrasound: micro-Doppler photoacoustic effect and
detection by ultrasound
Fei Gao1,*, Xiaohua Feng1, Yuanjin Zheng1, and Claus-Dieter Ohl2
1
School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore
2
School of Physical and Mathematical Sciences, Nanyang Technological University, 639798, Singapore
*
Corresponding author: [email protected]
Abstract:
In recent years, photoacoustics has attracted intensive research for both anatomical and
functional biomedical imaging. However, the physical interaction between photoacoustic
generated endogenous waves and an exogenous ultrasound wave is a largely unexplored area.
Here, we report the initial results about the interaction of photoacoustic and external
ultrasound waves leading to a micro-Doppler photoacoustic (mDPA) effect, which is
experimentally observed and consistently modelled. It is based on a simultaneous excitation
on the target with a pulsed laser and continuous wave (CW) ultrasound. The thermoelastically
induced expansion will modulate the CW ultrasound and leads to transient Doppler frequency
shift. The reported mDPA effect can be described as frequency modulation of the intense CW
ultrasound carrier through photoacoustic vibrations. This technique may open the possibility
to sensitively detect the photoacoustic vibration in deep optically and acoustically scattering
medium, avoiding acoustic distortion that exists in state-of-the-art pulsed photoacoustic
imaging systems.
1
Refractometric sensing of Li salt with visible-light Si3 N4 microdisk resonators
C. Doolin,a) P. Doolin, B.C. Lewis, and J.P. Davisb)
Department of Physics, University of Alberta, T6G 2E1 Edmonton, AB, Canada
arXiv:1412.7167v1 [cond-mat.mes-hall] 22 Dec 2014
(Dated: 24 December 2014)
We demonstrate aqueous refractive index sensing with 15 to 30 µm diameter silicon nitride microdisk resonators to detect small concentrations of Li salt. A dimpled-tapered fiber is used to couple 780 nm visible
light to the microdisks, in order to perform spectroscopy their optical resonances. The dimpled fiber probe
allows testing of multiple devices on a chip in a single experiment. This sensing system is versatile and easy
to use, while remaining competitive with other refractometric sensors. For example, from a 20 µm diameter
device we measure a sensitivity of 200 ± 30 nm/RIU with a loaded quality factor of 1.5 × 104 , and a limit of
detection down to (1.3 ± 0.1) × 10−6 RIU.
Optical whispering-gallery mode (WGM) resonators
are an area under avid research as they promise fast,
sensitive and label-free detection of chemical and biological samples.1–3 Sensors based on whispering-gallery mode
resonators have been used for the label-free detection
of single viruses,4,5 nanoparticles,6–9 single proteins10 ,
nucleotides,11,12 and are even used commercially.13 Many
geometries have been used for bulk refractometric sensing. For example, glass whispering gallery mode resonators such as microspheres14,15 and toriods7,10,16 exhibit ultra-high quality factors (Qs) of > 106 allowing
precise readout of optical mode wavelengths, and with
tens of nm/RIU sensitivity achieve detection limits of
10−7 refractive index units (RIU).14 Glass WGMs with
a hollow core, dubbed liquid core optical ring resonators
(LCORRs), have been shown to achieve gigantic sensitivities of 570 nm/RIU when carefully engineered such that
the optical mode sits largely in the liquid core instead
of the glass.17 With Qs of 105 these represent the best
bulk refractive index sensors in the literature, achieving
a limit of detection of 3.8×10−8 RIU.
LCORRs are remarkably impressive, but for the purposes of integration - such as into lab-on-a-chip devices
- it may be more useful to have WGM resonators fabricated on CMOS compatible chips. The commercially
proven silicon-on-insulator platform has been used to fabricate optical resonators in planar geometries, which allows for full integration. Simple planar WGM geometries such as disk18,19 or ring20–22 resonators have demonstrated sensitivities up to 160 nm/RIU with Qs up to
105 . Slot WGM resonators are of significant interest,
due to their ability to be engineered such that the optical mode lies mostly within the slot and outside the resonator medium23–25 demonstrating up to 298 nm/RIU24
but with Qs reaching only a couple thousand; photonic
crystal resonators utilize photonic bandgaps to highly localize the optical mode6,26 and have demonstrated 490
nm/RIU sensitivities with similar Qs.
Here we demonstrate an attractive permutation of an
on-chip WGM resonator to be used for refractive index
a) [email protected]
b) [email protected]
sensing - a thin silicon nitride microdisk resonator.27,28
Si3 N4 is a desirable material for optical sensing due
to its CMOS compatibility,29 transparency to visible
light, and lower refractive index than silicon resulting in less mode confinement.30 Si3 N4 refractometric
sensors have been described previously in optical ring
and slot geometries,23,25,31 and with optimization have
achieved sensitivities of 246 nm/RIU and detection limits of 5 × 10−6 RIU.25 Here we exploit silicon nitride’s
transparency to 780 nm laser light to enable large portions of the optical field to be in water, negating much of
the optical absorption caused by water at longer wavelengths. Using thin (< 150 nm) on-chip Si3 N4 microdisks
and an under-cut geometry to lower mode confinement,
sensitivities of > 200 nm/RIU and a limit of detection of
∼1×10−6 RIU are measured. This responsiveness results
(a)
(b)
(c)
(d)
FIG. 1. (a) Scanning electron microscope image of 20 µm
and 30 µm microdisks. Scale bar 5 µm. (b) Side view of a
dimpled-tapered fiber for visible light used to couple to individual microdisks. Scale bar 100 µm. (c) A representative
∼140 µL water droplet deposited on a chip of microdisks. The
tapered fiber is visible in the droplet touching the chip. Scale
bar 2 mm. (d) The dimpled-tapered fiber is used to selectively
couple light into a 20 µm microdisk. On resonance, light in
the mode is visible due to surface scattering. Scale bar 10
µm.
Hybrid Superconducting Neutron Detectors
V. Merlo1, M. Salvato1,2, M. Cirillo1,2, M. Lucci1, I. Ottaviani1, A. Scherillo3,
G. Celentano4 and A. Pietropaolo4,5*
1 Dipartimento di Fisica, Università Tor Vergata, Via della Ricerca Scientifica, I-00133 Roma, Italy
2 CNR-SPIN, Italy
3 Science and Technology Facility Council, ISIS Facility Chilton Didcot Oxfordshire, UK
4 ENEA Frascati Research Centre, V. E. Fermi 45, 00044 Frascati, Italy
5 Mediterranean Institute of Fundamental Physics
A new neutron detection concept is presented that is based on superconductive niobium (Nb)
strips coated by a boron (B) layer. The working principle of the detector relies on the nuclear
reaction
10
B  n    7Li , with  and Li ions generating a hot spot on the current-biased Nb strip
which in turn induces a superconducting-normal state transition. The latter is recognized as a
voltage signal which is the evidence of the incident neutron. The above described detection
principle has been experimentally assessed and verified by irradiating the samples with a pulsed
neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated
superconducting strips, kept at a temperature T = 8 K and current-biased below the critical current
Ic, are driven into the normal state upon thermal neutron irradiation. As a result of the transition,
voltage pulses in excess of 40 mV are measured while the bias current can be properly modulated to
bring the strip back to the superconducting state, thus resetting the detector. Measurements on the
counting rate of the device are presented and the future perspectives leading to neutron detectors
with unprecedented spatial resolutions and efficiency are highlighted.
PACS numbers: 29.40.-n, 07.57.Kp, 28.20.Fc
*Corresponding author: [email protected]
1 Imprints of CP-violating phases induced by sterile neutrinos in T2K
N. Klop∗ and A. Palazzo
arXiv:1412.7524v1 [hep-ph] 23 Dec 2014
Max-Planck-Institut für Physik (Werner Heisenberg Institut), Föhringer Ring 6, 80805 München, Germany
We investigate the impact of light (∼ eV) sterile neutrinos in the long-baseline experiment T2K.
We show that, within the 3+1 scheme, for mass-mixing parameters suggested by the short-baseline
anomalies, the interference among the sterile and the atmospheric oscillation frequencies induces
a new term in the νµ → νe transition probability, which has the same order of magnitude of
the standard 3-flavor solar-atmospheric interference term. We find that current T2K data, taken
together with the results of the θ13 -dedicated reactor experiments, are sensitive to two of the three
CP-violating phases involved in the 3+1 scheme. Both the standard CP-phase and the new one (δ ≡
δ13 and δ14 in our parameterization choice) tend to have a common best fit value δ13 ≃ δ14 ≃ −π/2.
Quite intriguingly, the inclusion of sterile neutrino effects leads to a better agreement among the
two estimates of θ13 obtained, respectively, from reactors and T2K, which in the 3-flavor framework
are slightly different.
PACS numbers: 14.60.Pq, 14.60.St
I.
INTRODUCTION
Neutrino physics is entering a new era. The discovery
of a relatively large value of the long-sought third mixing
angle θ13 has raised hopes of completing the picture of
the standard 3-flavor framework. The determination of
the two missing unknown properties, i.e., the amount (if
any) of leptonic CP-violation (CPV) and the neutrino
mass hierarchy (NMH) are now realistic targets.
CPV is a genuine 3-flavor phenomenon [1], which can
occur only if no pair of neutrino mass eigenstates is degenerate (m2i − m2j 6= 0 for i 6= j, i, j = 1, 2, 3) and if all
the three mixing angles (θ12 , θ23 , θ13 ) are non-zero. Now
that all these (six) necessary conditions are known to be
realized in Nature, the next task is to ascertain if a further (last) condition is fulfilled, i.e if the lepton mixing
matrix is non-real, or equivalently if the CP-phase δ is
different from 0 and π. The CP-phase δ is already being probed by the long-baseline (LBL) accelerator experiment T2K [2] (and also by MINOS [3] with less statistical power) in combination with the reactor θ13 -dedicated
experiments [4–7], which “fix” θ13 independently of δ.
Some (weaker) information on such a fundamental phase
is also provided by atmospheric neutrinos [8]. Quite intriguingly, all the latest global analyses [9–11] show a
weak indication (close to the 90% C.L.) of CPV, the best
fit value of the CP-phase being δ ∼ −π/2.
An apparently unrelated issue in present-day neutrino
physics is provided by the hints of light (∼ eV) sterile species suggested by the short-baseline (SBL) anomalies (see [12–14] for reviews). In the presence of sterile
neutrinos, the 3-flavor scheme must be enlarged so as to
include one (or more) mass eigenstates having non-zero
admixture with the active flavors. In such more general
frameworks, new CP-phases automatically appear and
∗ Now
at GRAPPA Institute, University of Amsterdam, Science
Park 904, 1098 XH Amsterdam, Netherlands
thus the question naturally arises as to wether the current and planned LBL experiments, designed to underpin
the standard CP-phase δ, have also some chance to detect
the new potential sources of CPV.1
In this work we show that the existing measurements of
νµ → νe appearance performed by the LBL experiment
T2K, taken in combination with those of ν̄e → ν̄e disappearance deriving from the θ13 -dedicated reactor experiments, are already able to provide information on the
non-standard sterile-induced CP-phases. In fact, differently from the SBL experiments, in LBL setups the oscillations induced by the new sterile neutrino species can
interfere with those driven by the two standard squaredmass splittings giving rise to observable effects. In particular, it turns out that the interference among the sterile and the atmospheric oscillation frequencies induces a
new term in the νµ → νe transition probability, which
has the same order of magnitude of the standard 3-flavor
solar-atmospheric interference term.
Working within the simple 3+1 scheme, we show that,
for mass-mixing parameters suggested by the current
SBL fits [13, 14], it is possible to extract quantitative information on two of the three CP-phases involved in the
model (one of them being the standard phase δ). Quite
intriguingly, the statistical significance of the information obtained on the new CP-phase is similar to that
achieved for the standard phase δ. In addition, our analysis evidences that the presence of 4-flavor effects tends
to resolve the slight tension (present within the 3-flavor
framework) between the two estimates of θ13 extracted,
respectively, from T2K and from reactors experiments.
The rest of the paper is organized as follows. In Sec. II
we introduce the theoretical framework needed to discuss
the analytical behavior of the LBL νµ → νe transition
probability in vacuum. In Sec. III we present the results
1
Previous work on the effects of light sterile neutrinos in LBL
setups can be found in [15–24].
X(3872) electromagnetic decay in a coupled-channel model∗
arXiv:1412.7406v1 [hep-ph] 23 Dec 2014
Marco Cardoso
CFTP, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
George Rupp
CFIF, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
Eef van Beveren
CFC, Departamento de Fı́sica, Universidade de Coimbra, Coimbra, Portugal
A multichannel Schrödinger equation with both quark-antiquark and
meson-meson components, using a harmonic-oscillator potential for q q̄ confinement and a delta-shell string-breaking potential for decay, is applied to
the axial-vecor X(3872) and lowest vector charmonia. The model parameters are fitted to the experimental values of the masses of the X(3872),
J/ψ and ψ(2S). The wave functions of these states are computed and then
used to calculate the electromagnetic decay widths of the X(3872) into
J/ψγ and ψ(2S)γ.
PACS numbers: 12.39.Pn,12.40.Yx,13.20.Gd,13.40.Hq
1. Introduction
The X(3872) was discovered in 2003 by the Belle Collaboration [1], and
later confirmed in CDF [2] and D0 [3] experiments. Its PDG[4] mass and
width are now MX = 3871.69 ± 0.17 MeV and ΓX < 1.2 MeV, respectively.
According to experiment it has quantum numbers J P C = 1++ [5] and I G =
0+ [6, 7]. The X(3872) seems to be difficult to describe as a simple cc̄ state.
Its main decays are into ρ0 J/ψ, ωJ/ψ and DDπ, with the latter final
state resulting mainly from an intermediate DD∗ channel. The first two
channels are OZI forbidden and the decay into ρ0 J/ψ also violates isospin
∗
Presented by M. Cardoso at the Workshop “EEF70”, Coimbra, Portugal, September
1–5, 2014
(1)
arXiv:1412.7405v1 [astro-ph.CO] 23 Dec 2014
Prepared for submission to JCAP
Light Sterile Neutrinos and
Inflationary Freedom
S. Gariazzoa,b C. Giuntib M. Lavederc
a
Department of Physics, University of Torino, Via P. Giuria 1, I–10125 Torino, Italy
INFN, Sezione di Torino, Via P. Giuria 1, I–10125 Torino, Italy
c
Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, and INFN, Sezione di
Padova, Via F. Marzolo 8, I–35131 Padova, Italy
b
E-mail: [email protected], [email protected], [email protected]
Abstract. We perform a cosmological analysis in which we allow the primordial power spectrum
of scalar perturbations to assume a shape that is different from the usual power-law predicted by the
simplest models of cosmological inflation. We parameterize the free primordial power spectrum with
a “piecewise cubic Hermite interpolating polynomial” (PCHIP). We consider a 3+1 neutrino mixing
model with a sterile neutrino having a mass at the eV scale, which can explain the anomalies observed
in short-baseline neutrino oscillation experiments. We find that the freedom of the primordial power
spectrum allows to reconcile the cosmological data with a fully thermalized sterile neutrino in the
early Universe. Moreover, the cosmological analysis gives us some information on the shape of the
primordial power spectrum, which presents a feature around the wavenumber k = 0.002 Mpc−1 .
cos(2φh −φS )
cos φS
Double Spin Asymmetries ALT
and ALT
in semi-inclusive DIS
Wenjuan Mao,1, 2 Zhun Lu,1, ∗ Bo-Qiang Ma,2, 3, 4, † and Ivan Schmidt5, ‡
1
arXiv:1412.7390v1 [hep-ph] 23 Dec 2014
2
Department of Physics, Southeast University, Nanjing 211189, China
School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
3
Collaborative Innovation Center of Quantum Matter, Beijing, China
4
Center for High Energy Physics, Peking University, Beijing 100871, China
5
Departamento de Fı́sica, Universidad Técnica Federico Santa Marı́a,
and Centro Cientı́fico-Tecnológico de Valparaı́so, Casilla 110-V, Valparaı́so, Chile
We investigate the double-spin asymmetries of pion production in semi-inclusive deep inelastic
scattering with a longitudinal polarized beam off a transversely polarized proton target. Particularly,
we consider the cos φS and cos(2φh − φS ) modulations, which can be interpreted by the convolution
of the twist-3 transverse momentum dependent distributions and twist-2 fragmentation functions.
Three different origins are taken into account simultaneously for each asymmetry: the gT D1 term,
⊥
⊥
⊥
the eT H1⊥ term, and the e⊥
T H1 term in the cos φS asymmetry; and the gT D1 term, eT H1 term, and
⊥ ⊥
eT H1 term in the cos(2φh − φS ) asymmetry. We calculate the four twist-3 distributions gT (x, kT2 ),
2
gT⊥ (x, kT2 ), eT (x, kT2 ), and e⊥
T (x, kT ) in a spectator-diquark model including vector diquarks. Then
we predict the two corresponding asymmetries for charged and neutral pions at the kinematics of
HERMES, JLab, and COMPASS for the first time. The numerical estimates indicate that the two
different angular-dependence asymmetries are sizable by several percent at HERMES and JLab, and
the cos φS asymmetry has a strong dependence on the Bjorken x. Our predictions also show that the
dominant contribution to the cos φS asymmetry comes from the gT D1 term, while the gT⊥ D1 term
gives the main contribution to the cos(2φh − φS ) asymmetry; the other two T -odd terms almost give
negligible contributions. Especially, the cos(2φh − φS ) asymmetry provides a unique opportunity to
probe the distribution gT⊥ .
PACS numbers: 12.39.-x, 13.60.-r, 13.88.+e
I.
INTRODUCTION
In the last two decades, azimuthal asymmetries in
spin-polarized semi-inclusive deeply inelastic scattering
(SIDIS) in the small transverse momentum region have
been explored extensively by experimental and theoretical studies (for reviews, see [1–4]). Of particular interest are the Sivers asymmetry [5–7] and the Collins
asymmetry [8], which have been measured by the HERMES Collaboration [9, 10], the COMPASS Collaboration [11–16] and the Jefferson Lab (JLab) Hall A Collaboration [17, 18]. These asymmetries provide great
opportunities to access novel distributions of unpolarized quark/hadron inside a transversely polarized nucleon/quark, and therefore, they are crucial for the understanding of the transverse spin and momentum structure of nucleon. Recently, further asymmetries beyond
the Sivers and Collins asymmetries also receive growing attentions, such as the sin(3φh − φS ) asymmetry [19]
that involves the pretzelosity distribution h1T (x, kT2 ) [20–
22], and the cos(φh − φS ) double spin asymmetry [23]
contributed by g1T (x, kT2 ) [24–26]. These are leadingtwist asymmetries. On the other hand, measurements
of several single-spin asymmetries(SSAs) appearing at
subleading-twist level, i.e., the longitudinally beam spin
∗ Electronic
address: [email protected]
address: [email protected]
‡ Electronic address: [email protected]
† Electronic
φh
asymmetry Asin
[27–30] and the longitudinal target
LU
sin φh
spin asymmetry AUL [31, 32], were also performed.
Sizable asymmetries have been observed and have provided the basis for several related theoretical studies [33–
39]. Here we should mention a recent theoretical prediction [40] on the transverse SSAs at subleading-twist.
These asymmetries are of vital importance, as they provide complementary information on the spin and flavor
structure of nucleon.
Encouraged by the sizable asymmetries in SSAs at
twist-3 level, in this work we will consider the case of double polarized SIDIS, in which a longitudinally polarized
lepton beam collides on a transversely polarized nucleon
target. Except for the aforementioned cos(φh −φS ) asymmetry that appears at leading twist, theoretically there
are two other angular modulations (assuming one photon
exchange), the cos φS and the cos(2φh − φS ) moments,
which may also receive non-vanishing contributions. As
shown in Ref. [41], by assuming tree-level TMD factorization, each of the two double spin asymmetries (DSAs) can
be interpreted as the convolution of twist-3 transverse
momentum dependent (TMD) distributios and fragmentation functions (FFs) and their twist-2 counterparts.
Since there are less systematic studies and calculations
on the cos φS and cos (2φh − φS ) asymmetries in the literature to reveal the related transverse spin structure of
the nucleon at twist 3, our main purpose is to give a phenomenological study on the feasibility of experimental
measurements on these transverse target DSAs at subleading twist. Particularly, we will focus on the roles
IPPP-14-111
DCP-14-222
MCNET-14-zzz
A theory perspective on Top2014
Frank Krauss
arXiv:1412.7343v1 [hep-ph] 23 Dec 2014
Institute for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, UK
Abstract: This is the write-up of the theory keynote talk on the Top2014 conference in
Cannes, France.
1
Introduction
It is widely appreciated that the top quark indeed is a very special particle, for a number of reasons. First of
all, it is the only strongly interacting fundamental particle, which does not experience the effect of asymptotic
freedom: due to its short lifetime it will always decay before the strong interactions can force it into a bound
state. This in itself makes it a highly interesting laboratory for precision studies of QCD in the perturbative
regime. Furthermore, and maybe even more importantly, its large mass guarantees the top quark to play
a dominant role in the running of the Higgs boson mass. This tight link to the electroweak symmetry
breaking sector renders a deeper and detailed understanding of all of its properties from quantum numbers
to interaction properties a cornerstone for our understanding of the particle universe, the fundamental laws
of physics at the smallest distances and largest energies. In this context it is somewhat amusing to note
that its couplings to the Higgs boson are perturbative although the ratio of the top mass to the vacuum
expectation value, mt /v is very close to unity. This makes a closer study of its coupling to the Higgs boson a
high priority in top physics, and in particular the confirmation of the predicted identity of physical top mass
and its Yukawa coupling Yt will provide an important test of the Standard Model. This, ultimately provided
by precision measurements of the tt̄H production rate and distributions, is a very challenging centrepiece of
the the physics programme at the Run II of the LHC. At the same time, it will also be important to confirm
that the element Vtb of the Cabibbo–Kobayashi–Maskawa (CKM) matrix indeed is close to one, as predicted
from the unitarity constraint of the very same matrix. This can be achieved by precision studies of single top
production at the LHC. In both cases, deviations from these relations, mt = Yt and Vtb ≈ 1, would directly
signal new physics. Lastly, due to its large mass, production of top quarks in various processes probably is
the most notorious background in nearly all searches for new physics and thereby a precise understanding of
processes leading to top quarks in the final state will be hugely important to find or constrain new physics
in direct searches.
In this contribution I will report on the fairly amazing progress in theory before the conference, discuss some
of the available tools, and will finally reflect on the progress on the experimental side.
2
Theory Progress: High-Precision
Probably the most notable progress on the theory side is the first complete calculation of the inclusive
top–pair cross section to next-to–next-to leading order (NNLO) accuracy in the strong coupling, reported
last year in [1]. Their result also forms the basis for a number of further calculations, which may further
arXiv:1412.7254v1 [hep-ph] 23 Dec 2014
Prepared for submission to JHEP
Model independent determination of the
CKM phase γ using input from D 0-D 0 mixing
Samuel Harnew and Jonas Rademacker
H H Wills Physics Laboratory, University of Bristol, UK
E-mail: [email protected], [email protected]
Abstract: We present a new, amplitude model-independent method to measure the
CP violation parameter γ in B − → DK − and related decays. Information on charm
interference parameters, usually obtained from charm threshold data, is obtained from
charm mixing. By splitting the phase space of the D meson decay into several bins,
enough information can be gained to measure γ without input from the charm threshold.
We demonstrate the feasibility of this approach with a simulation study of B − → DK −
with D → K + π − π + π − . We compare the performance of our novel approach to that
of a previously proposed binned analysis which uses charm interference parameters
obtained from threshold data. While both methods provide useful constraints, the
combination of the two by far outperforms either of them applied on their own. Such
an analysis would provide a highly competitive measurement of γ. Our simulation
studies indicate, subject to assumptions about data yields and the amplitude structure
of D 0 → K + π − π + π − , a statistical uncertainty on γ of ∼ 13◦ with existing data and
∼ 4◦ for the LHCb-upgrade.
CP3-14-85
A global approach to top-quark flavor-changing interactions
Gauthier Durieux,1, 2 Fabio Maltoni,2 and Cen Zhang3
arXiv:1412.7166v1 [hep-ph] 22 Dec 2014
1
Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853, USA
2
Centre for Cosmology, Particle Physics and Phenomenology,
Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
3
Department of Physics, Brookhaven National Laboratory, Upton, NY, 11973, USA
We adopt a fully gauge-invariant effective-field-theory approach for parametrizing top-quark
flavor-changing-neutral-current interactions. It allows for a global interpretation of experimental
constraints (or measurements) and the systematic treatment of higher-order quantum corrections.
We discuss some recent results obtained at next-to-leading order accuracy in QCD and perform, at
that order, a first global analysis of a subset of the available experimental limits in terms of effective
operator coefficients. We encourage experimental collaborations to adopt this approach and extend
the analysis by using all information they have prime access to.
I.
INTRODUCTION
The wealth of top quarks produced at the LHC has
moved top physics to a precision era. Detailed information on the top couplings, their strengths as well as
Lorentz structures, has been collected and possible deviations are being constrained. In addition, interactions that
are absent or suppressed in the Standard Model (SM)
become more and more accessible. Among these, topquark flavor-changing-neutral-current interactions (FCNCs) play a special role. Highly suppressed by the
Glashow-Iliopoulos-Maiani mechanism, the SM predicts
them to be negligible. Branching ratios for top FCNC
decays are notably of the order of 10−12 − 10−15 [1–3]
in the SM. Any evidence for such processes would thus
immediately point to new physics. In addition, the recent discovery of a scalar particle closely resembling the
SM Higgs boson [4, 5] has made Higgs-mediated FCNCs
experimentally searchable.
A wide variety of limits have been set on top-quark
FCNC interactions, see, e.g., Ref. [6]. Single top p,p- → t
production has been searched at the Tevatron by CDF [7]
and at the LHC by ATLAS [8, 9] while D0 [10, 11] and
CMS [12] considered the p,p- → tj production mode. In
addition, CMS also searched for single top production
in association with a photon [13] or a charged lepton
pair [14]. At LEP2, e+ e− → t j has been investigated
for by all four groups [15–19] while, at HERA, the single top e− p → e− t production has been considered by
ZEUS [20, 21] and H1 [22–24]. The FCNC decay processes, t → j `+ `− and t → j γ, have also been studied,
at the Tevatron by CDF [25–27] and D0 [28], and at
the LHC by ATLAS [29–31] and CMS [32, 33]. Finally,
t → j h has been constrained by CMS [34] that combined
the leptonic W W ∗ , τ τ , ZZ ∗ and γγ channels while ATLAS used the last (and most sensitive) one only [35, 36].
The effective field theory (EFT) [37–39] is a particularly relevant framework for parametrizing new physics
and has been used in many top-quark FCNC studies [40–
54]. It does not only incorporate all possible effects of
new heavy physics in a model-independent way, but also
order them and allows to consistently take into account
higher-order quantum corrections. Leading-order (LO)
predictions are actually insufficient when an accurate interpretation of observables in terms of theory parameters is aimed at. QCD corrections in top-decay processes [55–60] typically amount to approximately 10%,
while they can reach between 30% and 80% in production
processes [61–65]. The running and mixing of operator
coefficients should also be taken into account. While an
EFT description in principle requires a complete basis of
operators to be used, neglecting some of them may appear consistent when only lowest order estimates of specific processes are considered. The next-to-leading-order
(NLO) counterterms as well as the renormalization-group
(RG) running and mixings of operator coefficients however clearly reveal the unnatural and inconsistent character of neglecting some operators. A proper EFT description of new physics should necessarily be global. Currently, however, the limits obtained by experimental collaborations almost always assume one single FCNC interaction is present at the time.
The aim of this paper is to outline a general strategy for
studying top-quark interactions in the context of an EFT,
starting from the case of top-quark FCNC processes. Our
main points can be summarized as follows:
• The widely used formalism that relies on
dimension-four and five operators in the electroweak (EW) broken phase is inadequate from several respects.
• Calculations of FCNC processes can now be performed (in most cases already automatically) in the
EFT framework at NLO in QCD. Some new NLO
results for four-fermion operator contributions are
provided here for the first time.
• A consistent analysis should be global, i.e. , consider all operators contributing to a given process.
For such an approach to be successful a sufficiently
large (and complete) set of observables should be
identified. We show that for FCNC interactions
involving the top-quark this is already close to be
UdeM-GPP-TH-14-239
UMISS-HEP-2014-03
arXiv:1412.7164v1 [hep-ph] 22 Dec 2014
Simultaneous Explanation of the
RK and R(D (∗)) Puzzles
Bhubanjyoti Bhattacharya a,1 , Alakabha Datta b,2,
David London a,3 and Shanmuka Shivashankara b,4
a: Physique des Particules, Université de Montréal,
C.P. 6128, succ. centre-ville, Montréal, QC, Canada H3C 3J7
b: Department of Physics and Astronomy, 108 Lewis Hall,
University of Mississippi, Oxford, MS 38677-1848, USA
(December 24, 2014)
Abstract
At present, there are several hints of lepton flavor non-universality. The LHCb Collaboration has measured RK ≡ B(B + → K + µ+ µ− )/B(B + → K + e+ e− ), and the BaBar
Collaboration has measured R(D (∗) ) ≡ B(B̄ → D (∗)+ τ − ν̄τ )/B(B̄ → D (∗)+ ℓ− ν̄ℓ )
(ℓ = e, µ). In all cases, the experimental results differ from the standard model predictions by 2-3σ. Recently, an explanation of the RK puzzle was proposed in which
new physics (NP) generates a neutral-current operator involving only third-generation
particles. Now, assuming the scale of NP is much larger than the weak scale, this
NP operator must be made invariant under the full SU(3)C × SU(2)L × U(1)Y gauge
group. In this paper, we note that, when this is done, a new charged-current operator
can appear, and this can explain the R(D (∗) ) puzzle. A more precise measurement of
the double ratio R(D)/R(D ∗ ) can rule out this model.
1
[email protected]
[email protected]
3
[email protected]
4
[email protected]
2
Averages of b-hadron, c-hadron, and τ -lepton properties
as of summer 2014
arXiv:1412.7515v1 [hep-ex] 23 Dec 2014
Heavy Flavor Averaging Group (HFAG):
Y. Amhis1 , Sw. Banerjee2 , E. Ben-Haim3 , S. Blyth4 , A. Bozek5 , C. Bozzi6 ,
A. Carbone7,8 , R. Chistov9 , M. Chrząszcz5,10 , G. Cibinetto6 , J. Dingfelder11 ,
M. Gelb12 , M. Gersabeck13 , T. Gershon14 , L. Gibbons15 , B. Golob16,17 ,
R. Harr18 , K. Hayasaka19 , H. Hayashii20 , T. Kuhr12 , O. Leroy21 , A. Lusiani22 ,
K. Miyabayashi20 , P. Naik23 , S. Nishida24 , A. Oyanguren Campos25 , M. Patel26 ,
D. Pedrini27 , M. Petrič17 , M. Rama28 , M. Roney2 , M. Rotondo29 , O. Schneider30 ,
C. Schwanda31 , A. J. Schwartz32 , B. Shwartz33 , J. G. Smith34 , R. Tesarek35 ,
K. Trabelsi24,30 , P. Urquijo36 , R. Van Kooten37 , and A. Zupanc17
1 LAL,
3 LPNHE,
Université Paris-Sud, France
2 University of Victoria, Canada
Université Pierre et Marie Curie-Paris 6, Université Denis Diderot-Paris7, CNRS/IN2P3,
France
4 National United University, Taiwan
5 H. Niewodniczanski Institute of Nuclear Physics, Poland
6 INFN Ferrara, Italy
7 INFN Bologna, Italy
8 Universitá di Bologna, Italy
9 Institute for Theoretical and Experimental Physics, Russia
10 Universität Zürich, Switzerland
11 Bonn University, Germany
12 Karlsruher Institut für Technologie, Germany
13 The University of Manchester, UK
14 University of Warwick, UK
15 Cornell University, USA
16 University of Ljubljana, Slovenia
17 J. Stefan Institute, Slovenia
18 Wayne State University, USA
19 Nagoya University, Japan
20 Nara Women’s University, Japan
21 CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France
22 Scuola Normale Superiore and INFN, Pisa, Italy
23 University of Bristol, UK
24 KEK, Tsukuba, Japan
25 IFIC, University of Valencia, Spain
26 Imperial College London, UK
27 INFN Milano-Bicocca, Italy
28 INFN
30 Ecole
Frascati, Italy
29 INFN Padova, Italy
Polytechnique Fédérale de Lausanne (EPFL), Switzerland
31 Austrian Academy of Sciences, Austria
32 University of Cincinnati, USA
33 Budker Institute of Nuclear Physics, Russia
34 University of Colorado, USA
35 Fermilab, USA
36 University of Melbourne, Australia
37 Indiana University, USA
December 24, 2014
Abstract
This article reports world averages of measurements of b-hadron, c-hadron, and τ lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results
available through summer 2014. For the averaging, common input parameters used in
the various analyses are adjusted (rescaled) to common values, and known correlations
are taken into account. The averages include branching fractions, lifetimes, neutral meson
mixing parameters, CP violation parameters, parameters of semileptonic decays and CKM
matrix elements.
2
J/ψ measurements in the STAR experiment
Barbara Trzeciak1 (for the STAR Collaboration)
1
Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 115 19 Praha 1, Czech
Republic
v2
Abstract. In this paper, we present recent STAR J/ψ results. J/ψ nuclear modification factors
√
√
(RAA ) in Au+Au collisions at sN N = 200, 62.4 and 39 GeV and in U+U collisions at sN N = 193
GeV are measured and compared to different theoretical calculations. We also report J/ψ elliptic flow
√
(v2 ) results in Au+Au collisions at sN N = 200 GeV and the first ψ(2S) to J/ψ ratio measurement
√
in p + p collisions at s = 500 GeV.
Au+Au 200 GeV 0-80 %
0.1
It was proposed that quarkonia are dissociated in the
hot medium due to the Debye screening of the quarkantiquark potential and thus this ”melting” can be
a signature of Quark-Gluon Plasma (QGP) formation [1]. But there are other mechanisms that can alter
quarkonium yields in heavy-ion collisions relative to
p + p collisions, for example statistical recombination
of heavy quark-antiquark pairs in the QGP or cold
nuclear matter (CNM) effects. Systematic measurements of the quarkonium production for different colliding systems, centralities and collision energies may
help to understand the quarkonium production mechanisms in heavy-ion collisions as well as the medium
properties.
0
maximum non-flow
initially produced
coalescence from thermalized cc
initial + coalescence
initial + coalescence
hydrodynamic
-0.1
-0.2
0
2
4
6
T
1.8
1.6
A+A → J/ψ+X
STAR Au+Au
STAR (p > 5 GeV/c)
T
PHENIX Au+Au (|y|<0.35)
Zhao, Rapp
Zhao, Rapp (p > 5 GeV/c)
T
Liu et al.
Liu et al. (p > 5 GeV/c)
sNN = 200 GeV
0.07
'
Bψ (2s)dσ (ψ (2s))/B
RAA
1.2
HERA-B (e channel ), 42GeV, EPJC49, 545
HERA-B (µ channel), 42GeV, EPJC49, 545
PHENIX, 200GeV, PRD85, 092004
CDF, 1.8TeV, PRL79, 572
STAR 500GeV, this analysis
J/ψ
dσ(J/ψ )
1.4
0.08
0.06
8
10
p (GeV/c)
√
Figure 2. J/ψ v2 in Au+Au collisions at sN N = 200
GeV at mid-rapidity in 0-80% central events [2] with
different model predictions ([3–6]). The gray boxes
represent a non-flow estimation.
2 J/ψ and ψ(2S) measurements
T
1
0.8
0.6
0.05
0.04
0.4
0.03
0.2
0
0.02
0.01
50
100
150
1
2
3
4
5
6
7
200
250
300
350
Npart
STAR preliminary
0
0
8
9
pT (GeV/c)
Figure 3. J/ψ RAA as a function of Npart in Au+Au
√
collisions at sN N = 200 GeV at mid-rapidity ([7, 8])
with two model predictions ([9, 10]). The low-pT (< 5
GeV/c) result is shown as black full circles and the
high-pT (> 5 GeV/c) measurement as red full circles.
Figure 1. Ratio of ψ(2S) to J/ψ in p + p collisions at
√
s = 500 GeV from STAR (red circle) compared to
results from other experiments at different energies.
other experiments at different colliding energies, in
p + p and p+A collisions. The STAR data point is
consistent with the observed trend, and no collision
energy dependence of the ψ(2S) to J/ψ ratio is seen
with current precision.
√
In Au+Au collisions at sN N = 200 GeV STAR
has measured J/ψ pT spectra for different centrality
bins [7, 8]. It was found that at low pT (. 2 GeV/c)
the J/ψ pT spectra are softer than the Tsallis BlastWave prediction, assuming that J/ψ flows like lighter
hadrons [8]. This suggests that recombination may
contribute to low-pT J/ψ production. Measurement
STAR has measured J/ψ pT spectra
√ [7, 11] and
polarization [12] in p + p collisions at s = 200 GeV
via the dielectron decay channel (Bee = 5.9%) at midrapidity (|y| < 1). These results are compared to different model predictions to understand J/ψ production mechanism in elementary collisions. In order to
further test the charmonium production mechanism
and constrain the feed-down contribution from the excited states to the inclusive J/ψ production, the J/ψ
and
√ ψ(2S) signals were extracted in p + p collisions at
s = 500 GeV. Figure 1 shows ψ(2S)/J/ψ ratio from
STAR (red full circle) compared to measurements of
18th Conference of Czech and Slovak Physicists, Olomouc, Czech Republic, September 16–19, 2014
RAA
arXiv:1412.7345v1 [hep-ex] 23 Dec 2014
1 Introduction
√
ment in U+U collisions at sN N = 193 GeV as a full
circle. In U+U collisions one can reach up to 20%
higher energy density compared to Au+Au collisions
in the same centrality bin [14]. No difference in suppression compared to other measurements presented
in Fig. 4 is observed.
2
1.8
A+A → J/ ψ + X
Zhao-Rapp 200 GeV
Zhao-Rapp 62.4 GeV
Zhao-Rapp 39 GeV
Ncoll uncertainties
p+p 62.4 GeV uncertainty
p+p 39 GeV uncertainty
p+p 200 GeV stat. uncert.
Au+Au 200 GeV
1.6
Au+Au 62.4 GeV
1.4
Au+Au 39 GeV
1.2
U+U 193 GeV MinBias
1
0.8
3 Summary
0.6
0.4
0.2
0
0
In summary, significant suppression of low pT J/ψ is
seen in Au+Au collisions at various colliding energies:
√
sN N = 200, 62.4 and 39 GeV, and in U+U colli√
sions at sN N = 193 GeV. No strong energy dependence of the J/ψ suppression in Au+Au is observed.
√
Also, high-pT J/ψ in Au+Au collisions at sN N =
200 GeV are strongly suppressed in central collisions,
which suggests the QGP formation. ψ(2S) to J/ψ ratio √
was measured for the first time in p + p collisions
at s = 500 GeV. When compared to results from
other experiments, no collision energy dependence of
the ratio is seen.
STAR Preliminary
50
100
150
200
250
300
350
400
Npart
Figure 4. J/ψ RAA as a function of Npart in Au+Au
√
collisions at sN N = 200 (black), 62.4 (red) and 39
(blue) GeV at mid-rapidity with model predictions ([9]).
As the green circle the minimum bias U+U measurement
√
at sN N = 193 GeV is also presented.
of J/ψ v2 may provide additional information about
the J/ψ production mechanisms. Figure 2 shows J/ψ
√
v2 measured in STAR in Au+Au collisions at sN N
= 200 GeV [2]. At pT > 2 GeV/c v2 is consistent with
zero. Compared to different model predictions [3–6],
data disfavor the scenario that J/ψ with pT > 2 GeV/c
are dominantly produced by recombination (coalescence) from thermalized cc̄ pairs. Figure 3 shows J/ψ
RAA as a function of the number of participant nucle√
ons (Npart ) in Au+Au collisions at sN N = 200 GeV,
separately for low- (< 5 GeV/c) [8] and high-pT (> 5
GeV/c) [7] regions. Suppression increases with collision centrality and the RAA at high pT is systematic
higher than the low-pT one. The strong suppression
of high-pT J/ψ observed in central collisions (0-30%)
indicates color screening or other QGP effects – at
pT > 5 GeV/c J/ψ are expected to be less affected
by the recombination and CNM effects. The RAA results are compared with two models, Zhao and Rapp
[9] and Liu et al. [10]. Both models take into account
direct J/ψ production with the color screening effect
and J/ψ produced via the recombination of c and c̄
quarks. The Zhao and Rapp model also includes the
J/ψ formation time effect and the B-hadron feed-down
contribution. At low pT both predictions are in agreement with the data, while the high-pT result is well
described by the Liu et al. model and the model of
Zhao and Rapp underpredicts the measured RAA .
Low-pT J/ψ RAA measurements in Au+Au col√
lisions at various colliding energies:
sN N = 200
(black), 62.4 (red) and 39 (blue) GeV are shown in
Fig. 4. Within the uncertainties, a similar level of
suppression is observed for all three energies, which
can be described by the model predictions of Zhao
and Rapp [9]. However, it should be noted that due
to lack of precise p + p measurements at 62.4 and 39
GeV Color Evaporation Model calculations [13] are
used as baselines, which introduce large uncertainties.
Figure 4 also shows the Minimum Bias RAA measure-
Acknowledgements
This publication was supported by the European social fund within the framework of realizing the project
„Support of inter-sectoral mobility and quality enhancement of research teams at Czech Technical University in Prague”, CZ.1.07/2.3.00/30.0034.
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2
arXiv:1412.7341v1 [hep-ex] 23 Dec 2014
J/ψ and ψ(2S) measurement in p+p collisions at
200 and 500 GeV in the STAR experiment
√
s=
Barbara Trzeciak1 for the STAR Collaboration
1
Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague,
Brehova 7, 115 19 Praha 1, Czech Republic
E-mail: [email protected]
Abstract. In this paper, results on the J/ψ cross section and polarization measured via the
√
dielectron decay channel at mid-rapidity in p + p collisions at s = 200 and 500 GeV in the
√
STAR experiment are discussed. The first measurement of ψ(2S) to J/ψ ratio at s = 500
GeV is also reported.
1. Introduction
J/ψ and ψ(2S) are bound states of charm (c) and anti-charm (c) quarks. Charmonium physical
states have to be colorless, however they can be formed via a color-singlet (CS) or color-octet
(CO) intermediate cc state. One of the first models of the charmonium production, the Color
Singlet Model (CSM) [1], assumed that J/ψ is created through the color-singlet state only. This
early prediction failed to describe the measured charmonium cross section which has led to the
development of new models. For example, Non-Relativistic QCD (NRQCD) [1] calculations were
proposed in which a cc color-octet intermediate states, in addition to a color-singlet states, can
bind to form charmonia.
However, the charmonium production mechanism in elementary particle collisions is not
yet exactly known. For many years measurements of the J/ψ cross section have been used
to test different J/ψ production models. While many models can describe relatively well
the experimental data on the J/ψ cross section in p + p collisions [2–9], they have different
predictions for the J/ψ polarization. Therefore, measurements of the J/ψ polarization may
allow to discriminate among different models and provide new insight into the J/ψ production
mechanism.
2. Charmonium measurements in STAR
In STAR, charmonia have been measured so far via the dielectron decay channel. The STAR
detector [10] is a multi-purpose detector that has large acceptance at mid-rapidity, |η| < 1
with a full azimuthal coverage. Electrons can be identified using the Time Projection Chamber
(TPC) [11] through ionization energy loss (dE/dx) measurement. The Time Of Flight (TOF)
detector [12] greatly enhances the electron identification capability at low momenta where the
dE/dx bands for electrons and hadrons cross each other. At high pT , electron identification can
be improved by the Barrel Electromagnetic Calorimeter (BEMC) [13] which measures electron
energy and shower shape. The BEMC is also used to trigger on high-pT electrons (HT trigger).
Minimum Bias (MB) events are triggered by the Vertex Position Detectors (VPD) [14].
arXiv:1412.7317v1 [hep-ex] 23 Dec 2014
Pentaquark Θ+ search at HERMES
N. Akopov,26 Z. Akopov,6 W. Augustyniak,25 R. Avakian,26 A. Avetissian,26 E. Avetisyan,6 S. Belostotski,19
H.P. Blok,18, 24 A. Borissov,6 J. Bowles,14 V. Bryzgalov,20 J. Burns,14 G.P. Capitani,11 E. Cisbani,21 G. Ciullo,10
M. Contalbrigo,10 P.F. Dalpiaz,10 W. Deconinck,6 R. De Leo,2 E. De Sanctis,11 P. Di Nezza,11 G. Elbakian,26
E. Etzelmüller,13 R. Fabbri,7 A. Fantoni,11 L. Felawka,22 S. Frullani,21 D. Gabbert,7 J. Garay Garcı́a,6, 4
F. Garibaldi,21 G. Gavrilov,19, 6, 22 F. Giordano,15, 10 S. Gliske,16 M. Hartig,6 D. Hasch,11 Y. Holler,6 I. Hristova,7
Y. Imazu,23 A. Ivanilov,20 H.E. Jackson,1 S. Joosten,15, 12 R. Kaiser,14 G. Karyan,26 T. Keri,13, 14 E. Kinney,5
A. Kisselev,19 V. Kozlov,17 P. Kravchenko,9, 19 V.G. Krivokhijine,8 L. Lagamba,2 L. Lapikás,18 I. Lehmann,14
A. López Ruiz,12 W. Lorenzon,16 X. Lu,7 B.-Q. Ma,3 D. Mahon,14 S.I. Manaenkov,19 Y. Mao,3 B. Marianski,25
A. Martinez de la Ossa,5, 6 H. Marukyan,26 C.A. Miller,22 Y. Miyachi,23 A. Movsisyan,10, 26 M. Murray,14 E. Nappi,2
A. Nass,9 M. Negodaev,7 W.-D. Nowak,7 L.L. Pappalardo,10 R. Perez-Benito,13 A. Petrosyan,26 P.E. Reimer,1
A.R. Reolon,11 C. Riedl,15, 7 K. Rith,9 G. Rosner,14 A. Rostomyan,6 J. Rubin,1, 15 D. Ryckbosch,12 Y. Salomatin,20
G. Schnell,4, 12 K.P. Schüler,6 B. Seitz,14 T.-A. Shibata,23 M. Stancari,10 J.J.M. Steijger,18 S. Taroian,26
A. Terkulov,17 R. Truty,15 A. Trzcinski,25 M. Tytgat,12 Y. Van Haarlem,12 C. Van Hulse,4, 12 D. Veretennikov,19
V. Vikhrov,19 I. Vilardi,2 S. Wang,3 S. Yaschenko,6, 9 H. Ye,3 Z. Ye,6 S. Yen,22 B. Zihlmann,6 and P. Zupranski25
(The HERMES Collaboration)
1
Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843, USA
2
Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124 Bari, Italy
3
School of Physics, Peking University, Beijing 100871, China
4
Department of Theoretical Physics, University of the Basque Country UPV/EHU, 48080
Bilbao, Spain and IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
5
Nuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0390, USA
6
DESY, 22603 Hamburg, Germany
7
DESY, 15738 Zeuthen, Germany
8
Joint Institute for Nuclear Research, 141980 Dubna, Russia
9
Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
10
Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento
di Fisica e Scienze della Terra, Università di Ferrara, 44122 Ferrara, Italy
11
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
12
Department of Physics and Astronomy, Ghent University, 9000 Gent, Belgium
13
II. Physikalisches Institut, Justus-Liebig Universität Gießen, 35392 Gießen, Germany
14
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom
15
Department of Physics, University of Illinois, Urbana, Illinois 61801-3080, USA
16
Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA
17
Lebedev Physical Institute, 117924 Moscow, Russia
18
National Institute for Subatomic Physics (Nikhef ), 1009 DB Amsterdam, The Netherlands
19
B.P. Konstantinov Petersburg Nuclear Physics Institute, Gatchina, 188300 Leningrad Region, Russia
20
Institute for High Energy Physics, Protvino, 142281 Moscow Region, Russia
21
Istituto Nazionale di Fisica Nucleare, Sezione di Roma, Gruppo
Collegato Sanità and Istituto Superiore di Sanità, 00161 Roma, Italy
22
TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
23
Department of Physics, Tokyo Institute of Technology, Tokyo 152, Japan
24
Department of Physics and Astronomy, VU University, 1081 HV Amsterdam, The Netherlands
25
National Centre for Nuclear Research, 00-689 Warsaw, Poland
26
Yerevan Physics Institute, 375036 Yerevan, Armenia
(Dated: December 24, 2014)
The earlier search at HERMES for narrow baryon states excited in quasi-real photoproduction,
decaying through the channel pKS0 → pπ + π − , has been extended with improved decay-particle
reconstruction, more advanced particle identification, and increased event samples. The structure
observed earlier at an invariant mass of 1528 MeV shifts to 1522 MeV and the statistical significance
drops to about 2σ for data taken with a deuterium target. The number of events above background
is 68+98
−31 (stat) ± 13(sys). No such structure is observed in the hydrogen data set.
PACS numbers: 12.39.MK, 13.60.Rj, 14.20.Jn
Keywords: Glueball and nonstandard multi-quark, Pentaquark, Baryon production, Baryons
I.
INTRODUCTION
Exotic hadrons consisting of five quarks were proposed on the basis of quark and bag models [1–3] in
the early days of QCD. Predictions based on the Skyrme
model [4–7] generated renewed interest in the possible
December 24, 2014
1:31
WSPC Proceedings - 9.75in x 6.5in
proceedings
1
Diffraction physics with ALICE
at the LHC
arXiv:1412.7300v1 [hep-ex] 23 Dec 2014
Sergey Evdokimov for the ALICE collaboration
Institute for High Energy Physics of NRC ”Kurchatov Institute”,
Protvino, 142281, Russia
E-mail: [email protected]
The ALICE experiment is equipped with a wide range of detectors providing excellent
tracking and particle identification in the central region, as well as forward detectors
with extended pseudorapidity coverage, which are well suited for studying diffractive
processes. Cross section measurements of single and double diffractive processes per√
formed by ALICE in pp collisions at s = 0.9, 2.76, 7 TeV will be reported. Currently,
√
ALICE is studying double-gap events in pp collisions at s = 7 TeV, which give an
insight into the central diffraction processes: current status and future perspectives will
be discussed. The upgrade plans for diffraction studies, further extending the pseudorapidity acceptance of the ALICE setup for the forthcoming Run 2 of the LHC, will be
outlined.
Keywords: Diffraction; ALICE; LHC
1. Introduction
The total proton-proton cross section receives contributions from different processes. There are significant contributions from elastic scattering (∼ 26%), single (∼
12.5%), double (∼ 6.5%) and central (<1%) diffraction at the LHC energies 1 . These
processes usually acquires at low t-values and are subjects of non-perturbative QCD.
They also could be described in terms of the Regge theory in which proton-proton
scattering is interpreted as a Reggeon exchange in t-channel of the reaction. The
Regge pole approximation suggests a power-low growth of the total cross section
with a squared collision energy s:
α(0)−1
s
σtot ∼
,
(1)
s0
where α(t) is the Reggeon trajectory. Experimental studies have confirmed the cross
section growth with the collision energy, known as the Serpukhov effect 2 and confirmed to be universal for all hadrons at CERN 3,4 and Fermilab 5 . To describe this
effect, V.Gribov introduced 6 the so-called supercritical Pomeron trajectory with
the intercept α(0) > 1. All trajectories associated with known particles have intercepts α(0) < 1 and their contributions to the total cross section become negligible
at high energies 7 . Therefore, the Pomeron exchange dominates at high energies. In
this way, diffraction studies help in understanding the Pomeron nature and its connection to the soft QCD processes and vice versa. From the experimental point of
page 1
arXiv:1412.7176v1 [hep-ex] 22 Dec 2014
Measurement of the inclusive tt̄ cross section in the
LHC
Javier Brochero1 on behalf of the CMS and ATLAS Collaborations
1
Instituto de Fı́sica de Cantabria (IFCA-UC). Av. Los Castros, S/N Ed. Juan Jorda,
Santander, Spain
E-mail: [email protected]
Abstract. This document presents recent results of inclusive top-quark pair production cross
section measurements at 7 and 8 TeV. The results are obtained analyzing the data collected by
the CMS and ATLAS detectors at the LHC accelerator. Studies are performed in the dilepton
channel, where the smallest uncertainty is reached, with different approaches. The most precise
results of both experiments are combined and confronted with the most precise theoretical
calculation (NNLO-NNLL).
1. Introduction
The top quark, the heaviest fundamental particle with a mass about 173.3 GeV [1], plays an
important role in the study of the electroweak symmetry breaking (Higgs boson) as well as
in the search of physics beyond the standard model (BSM). Moreover, the production of top
quark anti-quark pairs is one of the main backgrounds in many of the processes related with the
standard model (SM) and BSM, and it is crucial to measure its production cross section with
very high precision.
The Large Hadron Collider (LHC) has been in operation since 2009, producing proton-proton
collisions with a center of mass energy of 7 TeV until 2011 and 8 TeV in 2012. This document
presents the most recent measurements of the inclusive tt̄ cross section with data collected using
the ATLAS [2] and the CMS [3] detectors.
The most recent theoretical predictions for the top quark pair production cross section
(σtt̄ ) are σtNNLO+NNLL
(8 TeV) = 245.9 ± 8.4 (scale) ± 11.3 (PDF) pb and σtNNLO+NNLL
(7 TeV) =
t̄
t̄
172.0 ± 5.8 (scale) ± 8.8 (PDF) pb [4] for a top-quark mass of mt = 173.3 GeV. According to
the SM, top quarks decay into a W boson and a b quark almost 100% of the times. This
leads to final states with two W bosons and two jets coming from the b quark fragmentation.
When both W bosons decay leptonically, the event contains two high momentum leptons with
opposite charge, two undetected neutrinos which are measured as missing energy in the plane
transverse to the beam axis (6 ET ), and at least two jets, where two of them originate from b
quarks. The dilepton channel is optimal to measure the inclusive tt̄ cross section due to the
small background contribution from other SM processes. As will be presented in the following
sections, the uncertainty on σtt̄ measurement in the dilepton channel is dominated by systematic
errors.
Deriving diffeomorphism symmetry
H. B. Nielsena , Astri Kleppeb
arXiv:1412.7497v1 [gr-qc] 21 Dec 2014
a
The Niels Bohr Institute, Copenhagen, Denmark, [email protected]
b
SACT, Oslo, Norway, [email protected]
Abstract
In an earlier article, we have ”derived” space, as a part of the Random Dynamics project.
In order to get locality we need to obtain reparametrization symmetry, or equivalently,
diffeomorphism symmetry.
There we sketched a procedure for how to get locality by first obtaining reparametrization
symmetry, or equivalently, diffeomorphism symmetry. This is the object of the present article.
1
Introduction
In an earlier article [1], we have ”derived” space, as a part of the Random Dynamics project
[2]. Since we want to have locality, we also need to derive reparametrization symmetry, or more
generally, diffeomorphism symmetry [3], essentially ensuring that the choice of coordinates plays
no role in the formulation of the physical laws.
We propose that diffeomorphism symmetry comes about as a result of a selection principle,
in reality a selection principle for how Nature ”chooses” its symmetry groups, a scheme that has
been developed by Holger Bech Nielsen and his collaborators [4]. The initial idea was that the
small representations of the Standard Model gauge group
SM G = S(U (2) × U (3))
(1)
is a signature of such a selection principle, singling out groups that have the “smallest” representations.
In the present article we use similar arguments, but instead of taking the Standard Model
group SM G = S(U (2) × U (3)) as the selected group, we consider the combined diffemorphismand-gauge group
B = {(λ, ϕ) |λ ∈ G, ϕ ∈ D}
(2)
where G is the group of all gauge transformations that map the four-dimensional spacetime
manifold M on the 12-dimensional manifold of SM G: the Lie group is a manifold,
λ : M → SM G
and D is the group of diffeomorphisms, a diffeomorphism ϕ given by a bijective differentiable
map
ϕ:M→M
1.1
An alternative to grand unified models
A major part of the success of the GUT SU (5) model is that the representations of the SU (5)
gauge group automatically represent the SU (5) subgroup S(U (2) ⊗ U (3)) with the Standard
1
arXiv:1412.7306v1 [hep-lat] 23 Dec 2014
OU-HET-829
KEK-CP-311
Effects of near-zero Dirac eigenmodes on axial U(1)
symmetry at finite temperature
Akio Tomiya∗1 , Guido Cossu2, Hidenori Fukaya1, Shoji Hashimoto2,3 , Junichi Noaki2
1 Department
of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka
560-0043, Japan
2 High Energy Accelerator Research Organization (KEK), Ibaraki 305-0801, Japan
3 School of High Energy Accelerator Science, The Graduate University for Advanced Studies
(Sokendai), Tsukuba 305-0801, Japan
E-mail: [email protected]
We study the axial U(1)A symmetry of Nf = 2 QCD at finite temperature using the Dirac eigenvalue spectrum. The gauge configurations are generated employing the Möbius domain-wall
fermion action on 163 × 8 and 323 × 8 lattices. The physical spatial size of these lattices is around
2 fm and 4 fm, respectively, and the simulated temperature is around 200 MeV, which is slightly
above the critical temperature of the chiral phase transition. Although the Möbius domain-wall
Dirac operator is expected to have a good chiral symmetry and our data actually show small values
of the residual mass, we observe significant violation of the Ginsparg-Wilson relation for the lowlying eigenmodes of the Möbius domain-wall Dirac operator. Using the reweighting technique,
we compute the overlap-Dirac operator spectrum on the same set of configurations and find a significant difference of the spectrum between the two Dirac operators for the low-lying eigenvalues.
The overlap-Dirac spectrum shows a gap from zero, which is insensitive to the spacial volume.
The 32nd International Symposium on Lattice Field Theory,
23-28 June, 2014
Columbia University New York, NY
∗ Speaker.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
http://pos.sissa.it/
Holographic description of confinement and screening through brane cosmology
F.A. Brito1,2 , D.C. Moreira1,2
1
Departamento de Fı́sica, Universidade Federal de Campina Grande,
Caixa Postal 10071, 58109-970 Campina Grande, Paraı́ba, Brazil
2
Departamento de Fı́sica, Universidade Federal da Paraı́ba,
arXiv:1412.7280v1 [hep-th] 23 Dec 2014
Caixa Postal 5008, 58051-970 João Pessoa, Paraı́ba, Brazil
We compute the holographic quark potential in the realm of brane cosmology. We show
that under certain conditions the very geometry due to an inflationary 3-brane induces a D3D7-brane system. The cosmological constant that appears involved in the original geometry
is attributed to the D7-brane position itself in its embedding process. We address the issues
of confinement at low distances, screening effects at sufficiently large distances, and quark
condensate.
I.
INTRODUCTION
In order to extend the AdS/CFT correspondence [1] to accomplish QCD-like theories one needs
to break supersymmetry and conformal invariance. The AdS/CFT correspondence is formulated
around the background geometry of a stack of N D3-branes where the strings may end — for a
review see [2–4]. The corresponding field theory is a gauge theory whose fields are in the adjoint
representation of SU (N ) group. To take into account flavor degrees of freedom one needs to add
Nf flavor branes. Now strings can be stretched between different types of branes with only one
charge under the SU (N ) group on the D3-branes and then describe quark fields. The corresponding
field theory now has fields (quarks) that are in the fundamental representation. One of the most
interesting set up to accomplish this is the D3-D7-brane system with Nf D7 flavor branes in the
probe limit (Nf ≪ N ) in order not to change the background geometry [5, 6]. Strings can have
both ends on the flavor brane to describe a dual to quark-antiquark operators since they are in the
adjoint representation of SU (Nf ) [2]. Such effort is one among several others in the direction to
achieve QCD-like theories.
In a general perspective one can think of this proposal as a way to ‘deform’ the AdS space. For
instance, for confining theories see [7–13]. In [14] was assumed a deviation from the conformal case
which is naturally obtained in geometries of brane cosmology scenarios [15, 16]. As we shall see,
a small deviation around AdS space controlled by the tension and the cosmological constant on
the brane is encoded on a fundamental constant C. It was found that such a deviation that leads
APCTP-Pre2014-016
arXiv:1412.7241v1 [hep-th] 23 Dec 2014
On the possibility of blue tensor spectrum
within single field inflation
Yi-Fu Caia, Jinn-Ouk Gongb,c, Shi Pib,
Emmanuel N. Saridakisd,e and Shang-Yu Wuf,g
a Department
of Physics, McGill University, Montréal, QC, H3A 2T8, Canada
Pacific Center for Theoretical Physics, Pohang 790-784, Korea
c Department of Physics, Postech, Pohang 790-784, Korea
d Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens, Greece
e Instituto de Fı́sica, Pontificia Universidad de Católica de Valparaı́so, Casilla 4950, Valparaı́so, Chile
f Department of Electrophysics, National Center for Theoretical Science,
National Chiao Tung University, Hsinchu 300, Taiwan
g Shing-Tung Yau Center, National Chiao Tung University, Hsinchu 300, Taiwan
b Asia
Abstract
We present a series of theoretical constraints on the potentially viable inflation models
that might yield a blue spectrum for primordial tensor perturbations. By performing a
detailed dynamical analysis we show that, while there exists such possibility, the corresponding phase space is strongly bounded. Our result implies that, in order to achieve a
blue tilt for inflationary tensor perturbations, one may either construct a non-canonical
inflation model delicately, or study the generation of primordial tensor modes beyond the
standard scenario of single slow-roll field.
Glue Spin SG in The Longitudinally Polarized
Nucleon
arXiv:1412.7168v1 [hep-lat] 22 Dec 2014
Raza Sabbir Sufian∗
Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506
E-mail: [email protected]
Michael J. Glatzmaier
E-mail: [email protected]
Yi-Bo Yang
E-mail:[email protected]
Keh-Fei Liu
E-mail:[email protected]
Mingyang Sun
Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506
[χQCD Collaboration]
We present a lattice QCD calculation of the glue spin SG in the nucleon for the first time. It was
recently shown that the first moment of the glue helicity distribution could be obtained through the
cross-product of the the electric field ~E and the physical gauge field ~A phys with the non-Abelian
R
Coulomb gauge condition, i.e. d 3 x ~E(x) × ~A phys (x) in the infinite momentum frame. We use the
gauge field tensor from the overlap Dirac operator to check the frame dependence and calculate
glue spin with several momenta. The calculation is carried out with valence overlap fermion on
2+1 flavor DWF gauge configurations on the 243 × 64 lattice with a−1 = 1.77 GeV with the light
sea quark mass corresponding to a pion mass of 330 MeV.
The 32nd International Symposium on Lattice Field Theory
23-28 June, 2014
Columbia University New York, NY
∗ Speaker.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
http://pos.sissa.it/
Raza Sabbir Sufian
Glue Spin SG in The Nucleon
1. Introduction
The complete decomposition of nucleon spin into its quark and glue components has been a
long challenging problem in QCD since the first discovery of ‘proton spin crisis’ [1]. To find out
where the spin of the proton comes from, it is expected that it should compose of the quark spin,
quark orbital angular momentum, glue spin, and glue orbital angular momentum in a sum rule
J = Sq + Lq + SG + LG
(1.1)
There has been a crucial question for a long time as to whether such a decomposition exists with
gauge-invariant local operators and, further more, if they can be measured experimentally. In this
work we particularly concentrate on the glue spin operator in regard to the feasibility of calculating
its matrix element on the lattice.
A recent calculation [2] of quark and glue momenta and angular momenta in the proton on a
quenched lattice has found quark spin contributes ∼ 25% [3], glue angular momentum contributes
∼ 28% and quark orbital angular momentum contributes ∼ 47% of proton spin based on the nucleon spin decomposition with the energy-momentum tensor in the Belafonte formalism [4]. In this
case, the glue angular momentum cannot be decomposed into spin and orbital angular momentum.
The next major question is if it is at all possible to decompose the glue total angular momentum into
its orbital and spin components as suggested in the canonical formalism, but in a gauge invariant
fashion.
A recent analysis [5] of high-statistics 2009 STAR [6] and PHENIX [7] data showed evidence
of non-zero glue helicity in the proton. For Q2 = 10 GeV 2 , they found gluon helicity distribution
∆g(x, Q2 ) positive and away from zero in the momentum fraction region 0.05 ≤ x ≤ 0.2. However,
the result presented in [5] has very large uncertainty in the small x-region.
In this work, we carry out a lattice calculation of the glue spin in the nucleon based on the theoretical framework in [8]. We shall present our preliminary result on the momentum dependence of the
glue spin in the nucleon.
2. Theoretical Framework
The total glue helicity which is the integral of the glue helicity distribution, i.e. ∆G =
is defined as [9],
R1
0
∆g(x)dx,
dξ − −ixP+ ξ −
+
e
hPS|Fa+α (ξ − )L ab (ξ − , 0)F̃α,b
(0)|PSi
(2.1)
2π
√
where the light front coordinates are ξ ± = (ξ 0 ± ξ 3 )/ 2. The proton plane wave state is written as
|PSi, with momentum Pµ and polarization Sµ . The dual gauge field tensor, "F̃ αβ = 12 ε αβ µν Fµν and
Z
∆G =
dx
i
2xP+
Z
the light cone gauge-link is in the adjoint representation L (ξ − , 0) = P exp −ig
R ξ−
0
A + (η − , 0⊥ )dη −
with A + ≡ T c A+
c . Eq. (2.1) is gauge invariant but its partonic interpretation is clear only in the
light cone gauge. One cannot evaluate this expression on the lattice due to its dependence on real
time, given by ξ − . After integrating the longitudinal momentum x, the light-cone operator for the
2
#
Yukawa couplings for intersecting D-branes on
non-factorisable tori
Stefan Förste and Christoph Liyanage
Bethe Center for Theoretical Physics
arXiv:1412.3645v2 [hep-th] 18 Dec 2014
and
Physikalisches Institut der Universität Bonn,
Nussallee 12, 53115 Bonn, Germany
Abstract
We compute Yukawa couplings in type IIa string theory compactified on a six-torus
in the presence of intersecting D6-branes. The six-torus is generated by an SO(12) root
lattice. Yukawa couplings are expressed as sums over worldsheet instantons. Our result
extends known expressions to a non-factorisable torus. As an aside we also fill in some
details for the factorisable torus and non-coprime intersection numbers.
Decay constants of the pion and its excitations in holographic QCD
Alfonso Ballon-Bayona∗
Centro de Fı́sica do Porto, Faculdade de Ciências da Universidade do Porto,
Rua do Campo Alegre 687, 4169-007 Porto, Portugal
Gastão Krein† and Carlisson Miller‡
arXiv:1412.7505v1 [hep-ph] 23 Dec 2014
Instituto de Fı́sica Teórica, Universidade Estadual Paulista,
Rua Dr. Bento Teobaldo Ferraz, 271 - Bloco II, 01140-070 São Paulo, SP, Brazil
We investigate the leptonic decay constants of the pion and its excitations with a 5-d holographic
model for quantum chromodynamics. We prove numerically that the leptonic decay constants of the
excited states of the pion vanish in the chiral limit when chiral symmetry is dynamically broken. This
nontrivial result is in agreement with a solid prediction of quantum chromodynamics and is based
on a generalized Gell-Mann-Oakes-Renner relationship involving the decay constants and masses of
the excited states of the pion. We also obtain an extended partially conserved axial-vector current
relation that includes the fields of the excited states of the pion, a relation that was proposed long
ago in the context of current algebra.
PACS numbers: 14.40.Be,14.40.-n,12.40.-y,11.15.Tk,11.25.Tq
I.
INTRODUCTION
There is a solid prediction of quantum chromodynamics (QCD) that the leptonic decay constant of the excited
states of the pion vanish in the chiral limit when chiral
symmetry is dynamically broken [1]. The real world is
not chirally symmetric, as the masses of the u and d
quarks are not zero. But these masses are much smaller
than the strong-interaction scale ΛQCD and it is therefore
natural to expect that the leptonic decay constants of the
excited states of the pion are dramatically suppressed in
nature. At first sight this prediction might seem surprising. Within a quark model perspective a suppression
of the leptonic decay constants for excited states is expected; the leptonic decay constant for an S-wave state
is proportional to the configuration-space wavefunction
at the origin and, compared to the ground state, excited
states have suppressed wavefunctions at the origin. However, within this perspective there is no obvious physical
mechanism that suggests a dramatic reduction of the decay constants for the excited states. The key point behind the suppression of the decay constants, as we shall
elaborate shortly ahead, is the dynamical breaking of chiral symmetry in QCD and the (pseudo) Goldstone boson
nature of the ground-state pion.
The suppression of the leptonic decay constants of
pion’s excited states is an interesting feature of nonperturbative QCD. Lattice QCD and models of nonperturbative QCD can benefit from this feature by using it as
a gauge to validate techniques and truncation schemes
in approximate calculations. A first lattice result from
2006 [2] for the pion’s first radial excitation, extrapo-
∗
†
‡
[email protected]
[email protected]
[email protected]
lated to the chiral limit, gives fπ1 /fπ0 ∼ 0.08 MeV; experimentally [3], fπ1 /fπ0 < 0.064 – the decay constant
of the n−th excited state is denoted in the present paper
by fπn and that of the ground state by fπ0 . At about
the same time, another lattice collaboration reports [4] a
very small value for fπ1 , with an extrapolated value to the
chiral limit consistent with zero. Finally, a very recent
publication [5] reports lattice results for the three lowest
excited states: fπ1 is modestly suppressed,fπ2 is significantly suppressed, and fπ3 ' fπ1 . Calculations based
on sum rules [6–8], effective chiral Lagrangians [9], and
a chiral quark model [10] also find strongly suppressed
values for fπ1 .
In recent years a new class of models for tackling nonpertubative problems in QCD has received great attention in the literature. These are holographic models inspired on the gauge-gravity duality, in that a strongly
coupled gauge theory in d dimensions is assumed to be
described equivalently in terms of a gravitational theory
in d + 1 dimensions. The assumed duality is based on the
Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence [11–13], a conjectured relationship between
conformal field theories and gravity theories in anti-de
Sitter spaces – for recent reviews, see Refs. [14, 15]. Although the holographic dual of QCD remains unknown,
there exist several models attempting to construct the
five-dimensional holographic dual of QCD by incorporating known nonperturbative features of QCD. Confinement, for example, can be modelled [16] by truncating
the AdS space with the introduction of an infrared cutoff
z0 ∼ 1/ΛQCD in the fifth dimension (the other four coordinates belong to the flat Minkowski spacetime). In such
a “hard-wall” model, one considers a slice 0 ≤ z ≤ z0
of AdS space, and imposes boundary conditions on the
fields at the infrared border z0 . Dynamical chiral symmetry breaking can be incorporated [17, 18] in the hard-wall
model with the use of scalar and vector fields in the AdS
space which are in correspondence, respectively, to the
arXiv:1412.7470v1 [hep-ph] 23 Dec 2014
WKB - type approximations in the theory of vacuum
particle creation in strong fields
S.A. Smolyansky∗, V.V. Dmitriev, A.D. Panferov and A.V. Prozorkevich
Saratov State University, Saratov, Russia
E-mail: [email protected], [email protected], [email protected]
D. Blaschke, L. Juchnowski
Institute for Theoretical Physics, University of Wroclaw, 50-204; Wroclaw, Poland
E-mail: [email protected], [email protected]
Within the theory of vacuum creation of an e+ e− - plasma in the strong electric fields acting in the
focal spot of counter-propagating laser beams we compare predictions on the basis of different
WKB-type approximations with results obtained in the framework of a strict kinetic approach.
Such a comparison demonstrates a considerable divergence results. We analyse some reasoning
for this observation and conclude that WKB-type approximations have an insufficient foundation
in the framework of QED in strong nonstationary fields. The results obtained in this work on the
basis of the kinetic approach are most optimistic for the observation of an e+ e− - plasma in the
range of optical and x-ray laser facilities. We discuss also the influence of unphysical features of
non-adiabatic field models on the reliability of predictions of the kinetic theory.
XXII International Baldin Seminar on High Energy Physics Problems,
15-20 September 2014
JINR, Dubna, Russia
∗ Speaker.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
WKB - type approximations
http://pos.sissa.it/
S.A. Smolyansky
1. Introduction
As it is known, the first predictions of the vacuum creation of an e+ e− - plasma (EPP) under
the action of a constant electric field appeared in the discussion of Klein’s paradox [1] based on
the interpretation as a tunnel effect [2, 3]. Recently, the tunneling mechanism has been applied to
predict chiral quasipartcile pair creation in graphene [4]. With the development of high-intensity
lasers the idea was raised to use strong laser fields for the verification of the "Schwinger effect" [5].
At the present time there are realistic projects for future experiments of such kind at high-power
laser facilities (see, e.g., Ref. [6]). These perspectives and the success of the Sauter-HeisenbergEuler prediction have excited hope that a similar approach could be used in the case of "laser" fields.
This resulted in the classical work by Brezin and Itzykson [7] and a series of works by V.S. Popov
[8] based on different versions of the WKB approximation in the QED of strong nonstationary
fields. In this context let us mention also the work [9]. On the other hand, there were also doubts
raised in the validity of WKB-type approaches to the case of fastly alternating fields expressed,
e.g., in [10].
The idea of the present work is to verify the correctness of the results of different WKBtype approaches for fast "laser" fields by using the strong kinetic equation (KE) approach [11] as
the basis. It is important that for a comparison we use the same nonadiabatic field model of a
periodical signal as in the works [7, 8, 9]. Such a comparison shows that one can speak at best
of a qualitative similarity in the asymptotic regions of low and high frequency of the electric field.
Differences become very large in the region of intermediate frequencies. We analyse some details
of this picture. On the other hand, the usage of the unphysical model of a nonadiabatic electric field
in the kinetic approach can lead to a considerable distortion of the EPP creation pattern.
2. Kinetic approach
Let us write the system of KE’s [12] as a system of ordinary differential equations (ODE)
1
f˙ = λ u, u̇ = λ (1 − 2 f ) − 2ε v, v̇ = 2ε u,
2
(2.1)
that is equivalent to the KE q
in the integro-differential form [11]. In Eq. (2.1) f (~p,t) is the dis-
tribution function, ε (~p,t) =
ε⊥2 + (p3 − eA(t))2 is the quasienergy of a charge particle in a time
q
dependent electric field of the linear polarization Aµ (t) = 0, 0, 0, A3 = A(t) , ε⊥ = m2 + p2⊥
is the transverse energy and λ (~p,t) = eE(t)ε⊥ /ε 2 is the amplitude of the vacuum excitation,
E(t) = −Ȧ(t).
We solve this system of ODE’s numerically with zero initial conditions f0 = u0 = v0 = 0 at
t = 0 for the nonadiabatic field model
E(t) = E0 sin ξ (t), A(t) = (E0 /ω ) cos ξ (t),
(2.2)
where ξ (t) = ω t + ϕ , ϕ is an initial phase. We are forced to use this unphysical field model as a
basic one in the wake of the works of the WKB direction. There are two limiting cases: 1) ϕ (1) = 0
(the field strength starts from zero, E(0) = 0, but with nonzero derivative, Ė(0) 6= 0, and A(0) 6= 0)
2
Influence of interactions on particle production
induced by time-varying mass terms
Seishi Enomoto∗, Olga Fuksińska† and Zygmunt Lalak‡
arXiv:1412.7442v1 [hep-ph] 23 Dec 2014
Institute of Theoretical Physics, University of Warsaw,
ul. Pasteura 5, 02-093 Warsaw, Poland
Abstract
We have investigated effects of interaction terms on non-perturbative particle
production. It is well known that time-varying masses induce abundant particle
production. In this paper we have shown that it is possible to induce particle production even if the mass term of a particle species is not varying in time. Such
particles are produced through the interactions with other fields, whose mass terms
are varying due to a time-dependent background. The necessary formalism has been
introduced and analytic and numerical calculations have been performed in a simple
but illustrative model. The rather general result is that the amount of produced particles without time-dependent masses can be comparable with the particle density
produced directly by the varying background if the strength of interaction terms is
reasonably large.
∗
e-mail: [email protected]
e-mail: [email protected]
‡
e-mail: [email protected]
†
arXiv:1412.7421v1 [hep-ph] 23 Dec 2014
FR-PHENO-2014-014
NLO QCD and electroweak corrections to W + γ production
with leptonic W-boson decays
Ansgar Denner1, Stefan Dittmaier2 , Markus Hecht2 , Christian Pasold1
1 Julius-Maximilians-Universität
Würzburg, Institut für Theoretische Physik und Astrophysik,
D-97074 Würzburg, Germany
2 Albert-Ludwigs-Universität
Freiburg, Physikalisches Institut,
D-79104 Freiburg, Germany
Abstract:
We present a calculation of the next-to-leading-order electroweak corrections to W + γ production, including the leptonic decay of the W boson and taking into account all off-shell effects of the
W boson, where the finite width of the W boson is implemented using the complex-mass scheme.
Corrections induced by incoming photons are fully included and find particular emphasis in the
discussion of phenomenological predictions for the LHC. The corresponding next-to-leading-order
QCD corrections are reproduced as well. In order to separate hard photons from jets, a quark-tophoton fragmentation function á la Glover and Morgan is employed. Our results are implemented
into Monte Carlo programs allowing for the evaluation of arbitrary differential cross sections. We
present integrated cross sections for the LHC at 7 TeV, 8 TeV, and 14 TeV as well as differential
distributions at 14 TeV for bare muons and dressed leptons. Finally, we discuss the impact of
anomalous W W γ couplings.
December 2014
GLAS-PPE/2014-05, MCnet-14-29, IPPP/14/111, DCPT/14/222
LHAPDF6: parton density access in the LHC precision era
Andy Buckleya,1 , James Ferrando1 , Stephen Lloyd2 , Karl Nordström1 ,
Ben Page3 , Martin Rüfenacht4 , Marek Schönherr5 , Graeme Watt6
1
School of Physics & Astronomy, University of Glasgow, UK
School of Physics & Astronomy, University of Edinburgh, UK
3
Departamento de Fı́sica Teórica y del Cosmos y CAFPE, Universidad de Granada, Spain
4
School of Informatics, University of Edinburgh, UK
5
Physik-Institut, Universität Zürich, Switzerland
6
Institute for Particle Physics Phenomenology, Durham University, UK
arXiv:1412.7420v1 [hep-ph] 23 Dec 2014
2
Received: date / Accepted: date
Abstract The Fortran LHAPDF library has been a
long-term workhorse in particle physics, providing standardised access to parton density functions for experimental and phenomenological purposes alike, following
on from the venerable PDFLIB package. During Run 1
of the LHC, however, several fundamental limitations
in LHAPDF’s design have became deeply problematic,
restricting the usability of the library for important
physics-study procedures and providing dangerous avenues by which to silently obtain incorrect results.
In this paper we present the LHAPDF 6 library,
a ground-up re-engineering of the PDFLIB/LHAPDF
paradigm for PDF access which removes all limits on use
of concurrent PDF sets, massively reduces static memory requirements, offers improved CPU performance,
and fixes fundamental bugs in multi-set access to PDF
metadata. The new design, restricted for now to interpolated PDFs, uses centralised numerical routines
and a powerful cascading metadata system to decouple software releases from provision of new PDF data
and allow completely general parton content. More than
200 PDF sets have been migrated from LHAPDF 5 to
the new universal data format, via a stringent quality
control procedure. LHAPDF 6 is supported by many
Monte Carlo generators and other physics programs, in
some cases via a full set of compatibility routines, and
is recommended for the demanding PDF access needs
of LHC Run 2 and beyond.
4
5
6
7
8
9
10
11
Usage examples . . . . . . . . . . . .
Data formats . . . . . . . . . . . . .
PDF uncertainties . . . . . . . . . .
PDF reweighting . . . . . . . . . . .
LHAPDF 5 / PDFLIB compatibility
Benchmarking and performance . . .
PDF migration and validation . . . .
Summary and prospects . . . . . . .
1
2
3
Introduction . . . . . . . . . . . . . . . . . . . . . . .
History and evolution of LHAPDF . . . . . . . . . .
Design of LHAPDF 6 . . . . . . . . . . . . . . . . . .
1
2
4
e-mail: [email protected]
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Parton density functions (PDFs) are a crucial input
into cross-section calculations at hadron colliders; they
encode the process-independent momentum structure
of partons within hadrons, with which partonic crosssections must be convolved to obtain physical results
that can be compared to experimental data. At leading
order in perturbation theory, PDFs encode the probability that a beam hadron’s momentum is carried by
a parton of given flavour and momentum fraction. At
higher orders this interpretation breaks down and positivity is no longer required – but PDF normalization at
all orders is constrained by the requirement that a sum
over all parton flavours i and momentum fractions x
equates to the whole momentum of the incoming beam
hadron B:
XZ
1
dx x fi/B (x; Q2 ) = 1,
(1)
0
where fi/B (x; Q2 ) is the parton density function for
parton i in B, at a factorization scale Q. Conservation
of baryon number leads to a flavour sum rule,
Z
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1 Introduction
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Contents
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0
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dx fi/B (x; Q2 ) − f¯i/B (x; Q2 ) = ni ,
(2)
Constraining Absolute Neutrino Masses via Detection of
Galactic Supernova Neutrinos at JUNO
Jia-Shu Lu,∗ Jun Cao,† Yu-Feng Li,‡ and Shun Zhou§
arXiv:1412.7418v1 [hep-ph] 23 Dec 2014
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
Abstract
A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute
scale of neutrino masses mν via the detection of galactic supernova neutrinos at the Jiangmen
Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. The
upper bound on the absolute neutrino mass is found to be mν < (0.83 ± 0.24) eV at the 95%
confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and
standard deviation are shown to account for statistical fluctuations. For comparison, we find that
the bound in the Super-Kamiokande experiment is mν < (0.94 ± 0.28) eV at the same confidence
level. However, the upper bound will be relaxed when the model parameters characterizing the
time structure of supernova neutrino fluxes are not exactly known.
∗
Electronic address: [email protected]
†
Electronic address: [email protected]
Electronic address: [email protected]
‡
§
Electronic address: [email protected]
1
December 24, 2014 1:31 WSPC/INSTRUCTION FILE
BU-HEPP-14-08
arXiv:1412.7417v1 [hep-ph] 23 Dec 2014
Modern Physics Letters A
c World Scientific Publishing Company
RUNNING OF THE COSMOLOGICAL CONSTANT AND ESTIMATE OF ITS VALUE
IN QUANTUM GENERAL RELATIVITY
B.F.L. WARD
Department of Physics, One Bear Place # 97316, Baylor University,
Waco, Texas, 76798-7316, USA
bfl [email protected]
Received (Day Month Year)
Revised (Day Month Year)
We present the connection between the running of the cosmological constant and the estimate of its value in the
resummed quantum gravity realization of quantum general relativity. We also address in this way some of the
questions that have been raised concerning this latter generalization and application of the original prescription
of Feynman for the formulation of quantum general relativity.
Keywords: quantum gravity; resummation; exact.
PACS Nos.: 04.60.Bc;04.62.+v;11.15.Tk
Contributed paper to the Special Issue: “Fundamental Constants in Physics and Their Time Variation”
(Modern Physics Letters A, Guest Ed. Joan Solà)
BU-HEPP-14-08, Nov., 2014
1. Introduction
As one can see in Refs. [1–9] there has been some controversy about the meaning of a running cosmological
constant in quantum field theory. In sum in Ref. [1], the invariance of the physical vacuum energy density
under renormalization group action is used to argue that the total response of this quantity to a change
in the renormalization scale, µ, is zero, so that it does not actually run. The authors in Ref. [2] argue
that, while the total response of the vacuum energy density to a change in such a scale is zero, this
still allows for that part of Einstein’s theory that we “see” at low energy to contribute to the implicitly
running part of the vacuum energy density, which is then compensated by the dependence on the running
scale due to both known contributions and unknown contributions from the possible UV completion of
Einstein’s theory. Here, we will present arguments that generally agree with this latter view and with
that in Ref. [9], where we use a UV finite approach [10–14] to quantum general relativity developed from
an extension of Feynman’s formulation [15, 16] of Einstein’s theory. This we do in the next Section a .
Having done this, we then show in Section 3 how the running of the cosmological constant and the
Newton constant are featured in a first principles estimate of the observed value of the cosmological
constant in the Planck scale cosmology scenario of Refs. [22]. Section 4 contains our summary remarks.
a We
need to stress that the arguments that are given in Ref. [1] do not disagree with those we present here, as we have
explained in Ref. [17], when “apples” are compared to “apples”.
Prepared for submission to JHEP
arXiv:1412.7400v1 [hep-ph] 23 Dec 2014
Mass spectra and decay properties of D Meson in a
relativistic Dirac formalism
Manan Shah,a,b Bhavin Patel,b P C Vinodkumara
a
Department of Physics, Sardar Patel University,
Vallabh Vidyanagar - 388 120, INDIA
b
P. D. Patel Institute of Applied Sciences, CHARUSAT,
Changa - 388 421, INDIA
E-mail: [email protected], [email protected],
[email protected]
Abstract: The mass spectra of ground as well as excited states of D meson are calculated
in the framework of a relativistic independent quark model. For the present study, we
have used the martin like potential for the quark confinement. Our predicted states in
S-wave, 2 3 S1 (2605.86 MeV) and 2 1 S0 (2521.72 MeV) are in very good agreement with
experimental result of 2608±2.4±2.5 MeV and 2539.4±4.5±6.8 MeV respectively reported
by BABAR Collaboration. The calculated P-wave D meson states, 13 P2 (2468.22 MeV),
13 P1 (2404.94 MeV), 13 P0 (2315.24 MeV) and 11 P1 (2367.94 MeV) are in close agreement
with experimental average (Particle Data Group) values results of 2462.6 ± 0.7 MeV, 2427 ±
26 ± 25 MeV, 2318 ± 29 MeV and 2421.3 ± 0.6 MeV respectively. The pseudoscalar decay
constant (fP = 202.57 MeV) of D meson obtained here is in very good agreement with
the experiment as well as with the lattice and other available theoretical predictions. The
Cabibbo favoured hadronic decay branching ratios, BR(D0 → K − π + ) and BR (D0 →
K + π − ) respectively as 3.835% and 1.069 × 10−4 are also in very good agreement with
the experimental values (CLEO Collaboration) of 3.91 ± 0.08% and (1.48 ± 0.07) × 10−4
respectively. Our predicted results in leptonic decay widths of D meson are also in better
accord with experiment as well as other theoretical results. The mixing parameters of
D0 − D̄0 oscillation, xq (5.14 ×10−3 ), yq (6.02 ×10−3 ) and RM (0.313 ×10−4 ) are in very
good agreement with BaBar and Belle Collaboration results.
GMCALC: a calculator for the Georgi-Machacek model∗
Katy Hartling†, Kunal Kumar‡, and Heather E. Logan§
Ottawa-Carleton Institute for Physics, Carleton University,
1125 Colonel By Drive, Ottawa K1S 5B6 Canada
arXiv:1412.7387v1 [hep-ph] 23 Dec 2014
Version 1.0: December 20, 2014
Abstract
The Georgi-Machacek model adds scalar triplets to the Standard Model Higgs sector in such a way
as to preserve custodial SU(2) symmetry in the scalar potential. This allows the triplets to have a nonnegligible vacuum expectation value while satisfying constraints from the ρ parameter. Depending on
the parameters, the 125 GeV neutral Higgs particle can have couplings to W W and ZZ larger than in
the Standard Model due to mixing with the triplets. The model also contains singly- and doubly-charged
Higgs particles that couple to vector boson pairs at tree level (W Z and like-sign W W , respectively).
GMCALC is a self-contained FORTRAN program that, given a set of input parameters, calculates
the particle spectrum and tree-level couplings in the Georgi-Machacek model, checks theoretical and
indirect constraints, and computes the branching ratios and total widths of the scalars. It also generates a
param card.dat file for MadGraph5 to be used with the corresponding FeynRules model implementation.
∗
Code available from http://people.physics.carleton.ca/∼logan/gmcalc/ .
[email protected][email protected]
§
[email protected]
†
1
Correlations between light and heavy flavors near the chiral crossover
Chihiro Sasaki1, 2 and Krzysztof Redlich2
arXiv:1412.7365v1 [hep-ph] 23 Dec 2014
2
1
Frankfurt Institute for Advanced Studies, D-60438 Frankfurt am Main, Germany
Institute of Theoretical Physics, University of Wroclaw, PL-50204 Wroclaw, Poland
(Dated: December 24, 2014)
Thermal fluctuations and correlations between the light and heavy-light mesons are explored
within a chiral effective theory implementing heavy quark symmetry. We show, that various heavylight flavor correlations indicate a remnant of the chiral criticality in a narrow range of temperature
where the chiral susceptibility exhibits a peak structure. The onset of the chiral crossover, in the
heavy-light flavor correlations, is therefore independent from the light flavors. This indicates that
the fluctuations carried by strange charmed mesons can also be used to identify the chiral crossover,
which is dominated by the non-strange light quark dynamics.
1.
2.
INTRODUCTION
Modifications in magnitude of fluctuations for different observables are usually considered as an excellent
probe of a phase transition or its remnant. In heavy-ion
collision, fluctuations related to conserved charges carried by light and strange quarks play an important role
to identify the QCD chiral crossover or deconfinement
properties [1, 2]. Recently, however, the Lattice QCD
simulations have revealed, that the charmed mesons are
deconfined together with light-flavor mesons in the temperature range where the chiral crossover is partly restored [3]. This result indicates that the light-flavor dynamics interferes non-trivially with the heavy flavors.
In the field theoretical approach, the physics of heavylight hadrons is constrained by heavy quark symmetry
which emerges in the heavy quark mass limit [4, 5]. The
pseudo-scalar and vector charmed mesons form the lowest
spin multiplets H, and their low-energy dynamics is dominated by interactions with Nambu-Goldstone bosons associated with spontaneous chiral symmetry breaking [6–
9]. The chiral partner of H is embodied as the secondlowest spin multiplets G [10, 11]. The mass splitting between G and H is proportional to the chiral order parameter, and its thermal/dense evolution characterizes partial restoration of the chiral symmetry in a medium [12–
16].
Recently, a self-consistent effective theory implementing the chiral and heavy quark symmetry has been formulated at finite temperature [15]. In the present paper,
we will use this effective theory to study the fluctuations
in various flavor sectors at finite temperature and vanishing chemical potential. Our special attention will be paid
to the properties of heavy-light mixed correlations to be
influenced by the underlying heavy quark symmetry in
the presence of the chiral crossover. We will show that
the onset of the chiral crossover is well identified in the
heavy-light flavor correlations, and that it is independent
from the light flavors.
EFFECTIVE LAGRANGIAN
We utilize the Lagrangian which includes the mesons
with the light and heavy flavors and their couplings.
To quantify the light-flavor dynamics, we introduce the
standard linear sigma model with three flavors. The
main building block is the chiral field Σ = T a Σa =
T a (σ a + iπ a ), expressed as a 3 × 3 complex matrix in
terms of the scalar σ a and the pseudoscalar π a states.
The Lagrangian is given by
with
LL = q̄ (i/
∂ − gT a (σ a + iγ5 π a )) q
+ tr ∂µ Σ† · ∂ µ Σ − VL (Σ) ,
(2.1)
2
VL = m2 tr Σ† Σ + λ1 tr Σ† Σ
h
2 i
+ λ2 tr Σ† Σ
− c det Σ + det Σ†
(2.2)
− tr h Σ + Σ† .
The U (1)A breaking effects in Eq. (2.2) are accommodated in the determinant terms, whereas the last term,
proportional to h = T a ha , breaks the chiral symmetry
explicitly.
Heavy-light meson fields, with negative and positive
parity, are introduced as [10, 11]
1 + v/ ∗ µ
Pµ γ + iP γ5 ,
2
1 + v/ G =
−iDµ∗ γ µ γ5 + D ,
2
H =
(2.3)
(2.4)
and chiral eigenstates are given via
1
HL,R = √ (G ± iHγ5 ) .
2
(2.5)
The relevant operators are transformed under the chiral
and heavy quark symmetries as
†
HL,R → SHL,R gL,R
,
Σ →
†
gL ΣgR
,
(2.6)
(2.7)
Preprint typeset in JHEP style - HYPER VERSION
HIP-2014-24/TH
Multi-Lepton Signatures of the Triplet Like Charged
Higgs at the LHC
Priyotosh Bandyopadhyaya,b,1 , Katri Huitua,2 and Aslı Sabancı Keçelia,3
arXiv:1412.7359v1 [hep-ph] 23 Dec 2014
a
Department of Physics, and Helsinki Institute of Physics,
P.O.Box 64 (Gustaf Hällströmin katu 2), FIN-00014 University of Helsinki, Finland
b
Dipartimento di Matematica e Fisica ”Ennio De Giorgi”, Universit‘a del Salento and
INFN, Via Arnesano, 73100, Lecce, Italy
Email: 1 [email protected],
[email protected],2 [email protected],
3
[email protected]
Abstract: We study multi-lepton signatures of the triplet like charged Higgs at the LHC
in the context of Y = 0 triplet extended supersymmetric model (TESSM). In TESSM
∓
the h±
i W Z coupling appears at tree level when the triplet vacuum expectation value
is nonzero, and because of the coupling the charged Higgs decay channels as well as the
production channels can dramatically change at the LHC. We show that for the triplet
dominated charged Higgs the main production channels are no longer through the top decay
or gg and gb fusions since these are very suppressed due to the lack of triplet-SM fermion
coupling. In the numerical analysis, we consider also other possible production channels
∓
some of which have additional contributions from the diagrams containing h±
i W Z vertex.
We investigate the decay channels of a triplet like light charged Higgs (mh± ≤ 200 GeV)
1
and show that depending on the triplet component, the charged Higgs can substantially
decay to W ± Z. We further examine the 3l, 4l, 5l multi-lepton signatures of the triplet
like charged Higgs by considering four different benchmark points for which we perform
PYTHIA level simulation using FastJet for jet formation at the LHC with 14 TeV. We
found that for favorable parameters the earliest discovery with 5σ signal significance can
appear with early data of 72 fb−1 of integrated luminosity. We also present the invariant
mass distribution Mlljj for (≥ 3`) + (6pT ≥ 30 GeV) and (≥ 3`) + (≥ 2j) + (6pT ≥ 30 GeV)
and show that in addition to the charged Higgs mass peak, an edge that carries information
about heavy intermediate neutral Higgs bosons arises at the end of the mass distribution.
Keywords: Higgs, Triplet Higgs, Supersymmetry, LHC.
arXiv:1412.7353v1 [hep-ph] 23 Dec 2014
Refined Applications of the
“Collapse of the Wavefunction”
L. Stodolsky
Max-Planck-Institut für Physik (Werner-Heisenberg-Institut)
Föhringer Ring 6, 80805 München, Germany
December 24, 2014
Abstract
In a two-part system the “collapse of the wavefunction” of one part
can put the other part in a state which would be difficult or impossible
to achieve otherwise, in particular one sensitive to small effects in the
‘collapse’ interaction.
We present some applications to the very symmeteric and experimentally accessible situations of the decays φ(1020) → K o K o , ψ(3770) →
Do Do , or Υ(4s) → B o B o , involving the internal state of the two-state K o
Do or B o mesons. The “collapse of the wavefunction” occasioned by a
decay of one member of the pair (‘away side’) fixes the state vector of that
side’s two-state system. Bose-Einstein statistics then determines the state
of the recoiling meson (‘near side’), whose evolution can then be followed
further.
In particular the statistics requirement dictates that the ‘away side’
and ‘near side’ internal wavefunctions must be orthogonal at the time of
the “collapse”. Thus a CP violation in the ‘away side’ decay implies a
complementary CP impurity on the ‘near side’, which can be detected
in the further evolution. The CP violation so manifested is necessarily
direct CP violation, since neither the mass matrix nor time evolution was
involved in the “ collapse”.
A parametrization of the direct CP violation is given and various manifestations are presented. Certain rates or combination of rates are identified which are nonzero only if there is direct CP violation.
The very explicit and detailed use made of “collapse of the wavefunction” makes the procedure interesting with respect to the fundamentals
of quantum mechanics. We note an experimental consistency test for our
treatment of the “collapse of the wavefunction”, which can be carried out
by a certain measurement of partial decay rates.
1
Introduction
The “collapse of the wavefunction”, where a ”measurement” suddenly fixes the
state of a quantum mechanical system, is one of the longest discussed and most
1
Neutrino oscillations and electron-capture storage-ring experiments
Walter Potzel∗
arXiv:1412.7328v1 [hep-ph] 23 Dec 2014
Physik-Department E15, Technische Universität München,
James-Franck-Str. 1, 85748 Garching, Germany
(Dated: December 24, 2014)
Oscillations in the electron-capture (EC) decay rate observed in storage-ring experiments are
reconsidered in connection with the neutrino mass difference. Taking into account that - according
to Relativity Theory - time is slowed down in the reference frame of the orbiting charged particles
as compared to the neutral particles (neutrinos) moving on a rectilinear path after the EC decay, we
derive a value of ∆m221 = (0.768 ± 0.012) · 10−4 eV 2 for the neutrino mass-squared difference which
fully agrees with that observed in other neutrino-oscillation experiments. To further check the
connection between EC-decay oscillations and ∆m221 we suggest experiments with different orbital
speeds, i.e., different values of the Lorentz factor.
PACS numbers: 14.60Pq, 03.30.+p, 29.20.Dh
1. Introduction
Several decay studies with highly-ionized nuclides
have been performed at the GSI Helmholtzzentrum für
Schwerionenforschung in Darmstadt [1], [2]. In the most
60+
recent and refined experiment hydrogen-like 142
61 P m
ions coasting p
at a velocity v (corresponding to a Lorentz
factor γ = 1/ 1 − v 2 /c2 = 1.42) in the ion storage ring
(ESR) were observed to decay by electron capture
142
60+
61 P m
60+
+ e− →142
+ νe
60 N d
(1)
60+
leaving a bare 142
nucleus and a neutrino in a
60 N d
two-body final state.
It was found that in such experiments the decay rate
R(t) - in addition to the exponential law - exhibits an
oscillatory time modulation. The decay can be described
by [2]
R(t) ∝ e−λt (1 + a · cos(ωt + φ)).
(2)
The best-fit values [2] were λ = 0.0130(8) s−1 , ω =
0.884(14) s−1 (period Tosc = 7.11(11) s), amplitude a =
0.107(24) and phase φ = 2.35(48) rad.
In the literature the question has been discussed if this
oscillatory modulation is connected to the mass eigenstates of the emitted neutrino. A fundamental theory
is still not available. However, it has been argued that
the final state after electron capture is a superposition
of two channels, which correspond to the two (neglecting
the third one) mass eigenstates (m1 , m2 ) of the neutrino,
resulting in an oscillatory frequency [2],[3]
ω21 = ∆m221 c2 /(2Mp h̄).
(3)
Here, ∆m221 = m22 − m21 is the mass-squared difference
of the two mass-eigenstate neutrinos [4], Mp is the mass
of the decaying parent nucleus, and h̄ and c are Planck’s
constant divided by 2π and the speed of light, respectively. Using ω21 = ω of ref. [2] and considering the
relativistic time dilatation it has been suggested:
∆m221 c4 = 2h̄ωγMp c2
(4)
However, eq. (4) gives a value ∆m221 = 2.19(3) · 10−4
eV2 /c4 , which is nearly three times larger than ∆m221 =
−4
(0.754+0.026
eV2 /c4 determined in a global fit of
−0.022 ) · 10
the results obtained in reactor and solar neutrino experiments [5].
There has been a long controversy in the literature
doubting the validity of eq. (3) on the basis of quantum
mechanics and, in particular, questioning the presence
of such interference effects in the decay rate observed in
electron-capture storage ring experiments (see, e.g., [3],
[6] - [15]). However, more recently, it was emphasized
[16], [17] that such oscillations in the EC decay rate might
indeed be caused by interference effects between the neutrino mass eigenstates due to indirect interaction of the
two mass eigenstates via their coupling to the decaying
ion, e.g., by the weak interaction [17] or by entanglement
[16]. At present a theoretical foundation of eq. ( 3) is
still unclear.
In the following we will not further discuss this issue,
but assume that such an indirect interaction (resulting in
eq. (3))does occur and concentrate on the time-dilatation
transformations according to Relativity Theory. We find
that after applying these transformations the value for
the neutrino mass-squared difference ∆m221 derived from
the EC storage-ring experiment is in full agreement with
∆m221 determined by reactor and solar neutrino measurements. To further examine this relation between ECdecay oscillations and ∆m221 additional experiments with
different orbital speed should be performed.
Preprint typeset in JHEP style - HYPER VERSION
KIAS-P14071/HIP-2014-23/TH
arXiv:1412.7312v1 [hep-ph] 23 Dec 2014
Lepton flavour violating signature in supersymmetric
U (1)0 seesaw models at the LHC
Priyotosh Bandyopadhyaya,b,1 , Eung Jin Chunc,1
a
Department of Physics, University of Helsinki and Helsinki Institute of Physics,
FIN-00014, Helsinki, Finland
b
Dipartimento di Matematica e Fisica ”Ennio De Giorgi”, Universit‘a del Salento and
INFN, Via Arnesano, 73100, Lecce, Italy
c
Korea Institute for Advanced Study, Seoul 130-722, Korea
Email: 1 [email protected],
[email protected], 2 [email protected]
Abstract: We consider a U (1)0 supersymmetric seesaw model in which a right-handed
sneutrino is a thermal dark matter candidate whose relic density can be in the right range
due to its coupling to relatively light Z̃ 0 , the superpartner of the extra gauge boson Z 0 . Such
light Z̃ 0 can be produced at the LHC through cascade decays of colored superparticles, in
particular, stops and sbottoms, and then decay to a right-handed neutrino and a sneutrino
dark matter, which leads to lepton flavor violating signals of same/opposite-sign dileptons
(or multileptons) accompanied by large missing energy. Taking some benchmark points,
we analyze the opposite- and same-sign dilepton signatures and the corresponding flavour
difference i.e., (2e − 2µ). It is shown that 5σ signal significance can be reached for some
benchmark points with very early data of ∼ 2 fb−1 integrated luminosity. In addition, 3`
and 4` signatures also look promising to check the consistency in the model prediction, and
it is possible to reconstruct the Z̃ 0 mass from jj` invariant mass distribution.
Chinese Physics C
Vol. xx, No. x (201x) xxxxxx
Decay rates and electromagnetic transitions of heavy quarkonia
J. N. Pandya1 , N. R. Soni1 , N. Devlani2 , A. K. Rai3
1
Applied Physics Department, Faculty of Technology & Engineering, The M S University of Baroda, Vadodara 390001, Gujarat, INDIA.
2 Applied Physics Department, Polytechnic, The M S University of Baroda, Vadodara 390002, Gujarat, INDIA.
arXiv:1412.7249v1 [hep-ph] 23 Dec 2014
3
Department of Applied Physics, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, INDIA.
Abstract: The electromagnetic radiative transition widths as well as digamma and digluonic decay widths for heavy
quarkonia are computed in the framework of extended harmonic confinement model (ERHM) and coulomb plus power
potential (CPPν ) with varying potential index ν. The outcome is being compared with the values obtained from
other theoretical models and the experimental results.
Key words: heavy quarkonia, radiative decays, electromagnetic transitions
PACS: 12.39.Jh; 12.39.Pn; 13.20.Gd
1
Introduction
Decay properties of mesons are of special experimental and theoretical interest because they provide us with
further insight on the dynamics of these system in addition to the knowledge we have gained from the spectra
of these families. Large number of experimental facilities
world over have provided and continue to provide enormous amount of data which needs to be interpreted using
available theoretical approaches [1]. Many phenomenological studies on numerous observables of the cc̄ and bb̄
bound states have established that the non-relativistic
nature appears to be an essential ingredient to understand the dynamics of heavy quarkonia [2]. Hence, heavy
quarkonium is characterized by the interplay among the
several supposedly well-separated scales typical of a nonrelativistic system: the heavy quark mass m, the inverse
of the typical size of the quarkonium 1/r ∼ mv and the
binding energy E ∼ mv 2 , where v ≪ 1 is the velocity of
the heavy quark inside the quarkonium. Two effective
field theories, non-relativistic QCD (NRQCD) [3, 4] and
potential NRQCD (pNRQCD) [5, 6], have also been developed. Applications of these two EFTs have led to a
plethora of new results for several observables in quarkonium physics [7].
Radiative transitions in heavy quarkonia have been
subject of interest as the CLEO-c experiment has measured the magnetic dipole (M1) transitions J/ψ(1S) →
γηc (1S) and J/ψ(2S) → γηc (1S) using combination of
inclusive and exclusive techniques and reconciling with
theoretical calculations of lattice QCD and effective field
theory techniques [8, 9]. M1 transition rates are normally
weaker than E1 rates, but they are of more interest because they may allow access to spin-singlet states that
are very difficult to produce otherwise. It is also inter-
esting that the known M1 rates show serious disagreement between theory and experiment when it comes to
potential models. This is in part due to the fact that
M1 transitions between different spatial multiplets, such
as J/ψ(1S) → γηc (2S → 1S) are nonzero only due to
small relativistic corrections to a vanishing lowest-order
M1 matrix element [10].
We use the spectroscopic parameters of extended
harmonic confinement model (ERHM) which has been
successful in prediction of masses of open flavour mesons
from light to heavy flavour sectors [11–13]. The mass
spectrum of charmonia and bottomonia predicted by
this model and a Coulomb plus Power Potential (CPPν )
with varying potential index ν (from 0.5 to 2.0) employing non-relativistic treatment for heavy quarks [14–17]
have been utilized for the present computations along
with other theoretical as well as experimental results.
2
Theoretical framework
One of the tests for the success of any theoretical model for mesons is the correct prediction of their
decay rates. Many phenomenological models predict
the masses correctly but overestimate the decay rates
[14, 15, 18]. We have successfully employed phenomenological harmonic potential scheme and Coulomb Plus
Power Potential (CPPν ) with varying potential index
for different confinement strengths to compute masses
of bound states of heavy quarkonia and the resulting parameters as well as wave functions have been used to
study various decay properties [13].
Choice of scalar plus vector potential for the quark
confinement has been successful in the predictions of the
low lying hadronic properties in the relativistic schemes
Received December 24, 2014
1) E-mail: [email protected]
010201-1
arXiv:1412.7246v1 [hep-ph] 23 Dec 2014
December 24, 2014 1:22 WSPC/INSTRUCTION FILE
BU-HEPP-14-09
Prediction for the Cosmological Constant in Resummed Quantum
Gravity and Constraints on SUSY GUT’s
B.F.L. Ward
Physics Department, Baylor University, One Bear Place # 97316
Waco, TX 76798-7316, USA
bfl [email protected]
Received Day Month Year
Revised Day Month Year
We use our resummed quantum gravity approach to Einstein’s general theory of relativity
in the context of the Planck scale cosmology formulation of Bonanno and Reuter to
estimate the value of the cosmological constant such that ρΛ = (0.0024eV )4 . We argue
that the closeness of this estimate to experiment constrains susy GUT models. We discuss
in turn various theoretical issues that have been raised about the approach itself as well
as about the application to estimate the cosmological constant. Given the closeness of
the estimate to the currently observed value, we also discuss the theoretical uncertainty
in the estimate – at this time, we argue it is still large.
Keywords: quantum gravity; resummation; exact.
04.60.Bc;04.62.+v;11.15.Tk
BU-HEPP-14-09, Nov., 2014
1. Introduction
As Weinberg1 has suggested, the general theory of relativity may have a non-trivial
UV fixed point, with a finite dimensional critical surface in the UV limit. This
would mean that it would be asymptotically safe1 with an S-matrix that depends
on only a finite number of observable parameters. In Refs.,2–12 Strong evidence
has been calculated in Refs.,2–12 using Wilsonian13–18 field-space exact renormalization group methods, to support Weinberg’s asymptotic safety hypothesis for the
Einstein-Hilbert theory.
In a parallel but independent development,19–28 we have shown29 that the extension of the amplitude-based, exact resummation theory of Ref.30–45 to the EinsteinHilbert theory leads to UV-fixed-point behavior for the dimensionless gravitational
and cosmological constants. In our development, we get the added bonus that the
resummed theory is actually UV finite when expanded in the resummed propagators and vertices to any finite order in the respective improved loop expansion. We
denote the attendant resummed theory as resummed quantum gravity.
1
Effects of Shock Waves on Neutrino Oscillations in Three Supernova Models
Jing Xu1∗ , Li-Jun Hu
1
1†
, Rui-Cheng Li1‡ , Xin-Heng Guo1§ and Bing-Lin Young2,3¶
College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, China
2
Department of Physics and Astronomy, Iowa State University, Ames, Iowa 5001, USA
3
Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
arXiv:1412.7240v1 [hep-ph] 23 Dec 2014
It has been realized that the shock wave effects play an important role in neutrino oscillations
during the supernova explosion. In recent years, with the development of simulations about supernova explosion, we have a better understanding about the density profiles and the shock waves in
supernovae than before. It has been shown that the appearance of shock waves not only varies with
time, but is also affected by the mass of the supernova. When the mass of the supernova happens to
be in a certain range (e.g. it equals 10.8 times the mass of the sun), there might be a reverse shock
wave, another sudden change of density except the forward shock wave, emerging in the supernova.
In addition, there are some other time-dependent changes of density profiles in different supernova
models. Because of these complex density profiles, the expression of the crossing probability at
the high resonance, PH , which we used previously would be no longer applicable. In order to get
more accurate and reasonable results, we use the data of density profiles in three different supernova
models obtained from simulations to study the variations of Ps (the survival probability of νe → νe ),
as well as Pc (the conversion probability of νx → νe ). It is found that the mass of the supernova
does make a difference on the behavior of Ps , and affects Pc at the same time. With the results
of Ps and Pc , we can estimate the number of νe remained after they go through the matter in the
supernova.
PACS numbers: 14.60.Pq, 13.15.+g, 25.30.Pt, 26.30.-k
I.
INTRODUCTION
Since 1980’s, supernova neutrinos have been a focus of our attention for a long time [1]-[3]. In recent years, the
issues about neutrino detection experiments and simulations of supernova explosion have always been hotspots in
scientific research fields [4]-[14]. Thanks to the results of simulations and development of theories on supernovae, the
whole process of supernova explosion has been understood much better now [13]-[16]. The post bounce period, one
stage in the process of supernova explosion, can be divided generally into the accretion phase and the cooling phase.
During the supernova explosion, both the collective effects and the shock wave effects play important roles in neutrino
oscillations [17][18]. As we know, in the post bounce period, a large number of supernova neutrinos go through the
supernova matter, carrying an enormous amount of energy, and emit from the supernova [19][20]. Meanwhile, the
∗
†
‡
§
¶
Email: [email protected]
Email: [email protected]
Email: Rui-cheng [email protected]
Corresponding author, Email: [email protected]
Email: [email protected]
A note on the newly observed Y (4220) resonance
R. Faccini∗,¶ , G. Filaci∗ , A.L. Guerrieri† , A. Pilloni∗,¶ , A.D. Polosa∗,¶
∗
Dipartimento di Fisica, “Sapienza” Università di Roma, P.le A. Moro 2, I-00185 Roma, Italy
¶
INFN sez. Roma 1, P.le A. Moro 2, I-00185 Roma, Italy
†
Dipartimento di Fisica and INFN, Università di Roma “Tor Vergata”,
Via della Ricerca Scientifica 1, I-00133 Roma, Italy
arXiv:1412.7196v1 [hep-ph] 22 Dec 2014
BES III Collaboration has recently observed a vector resonance in the χc0 ω channel, at a mass
of about 4220 MeV, named Y (4220). Hints of a similar structure appear in the hc π + π − channel.
We find that the two observations are likely due to the same state, which we identify with one of
the expected diquark-antidiquark resonances with orbital quantum number L = 1. This assignment
fulfills heavy quark spin conservation. The measured branching ratio of the Y (4220) into χc0 ω and
hc π + π − is compatible with the prediction for such a tetraquark state.
PACS numbers: 14.40.Rt, 12.39.Jh, 13.25.Gv
+ −
In a very recent
√ paper, the BES III Collaboration reports the e e → χcJ ω (J = 0, 1, 2) production cross section as
a function of s [1]. Hints of a resonant structure are present in the χc0 ω channel at ∼ 30 MeV above threshold (i.e.
at about 4220 MeV), whereas no evident structure appears in the χc1,2 ω channels. Some theoretical interpretations for
these peak have been proposed√[2]. BES Collaboration also reported the measurement of e+ e− → hc π + π − production
cross section as a function of s [3]. Hints of structures not compatible with the Y (4260) have been found [4]: in
particular a narrow peak at a mass ∼ 4220 MeV. In this mass region, many exotic charmonium-like states have been
identified according to the diquark-antidiquark model [5] (for a review, see [6]). In particular, the latest model [7]
predicts a tetraquark state, named Y3 , with quantum numbers J P C = 1−− , and mass and decay modes compatible
with a Y (4220) resonance. The wave function of this tetraquark state contains both heavy quark spin states, so it
can naturally decay into both χc0 ω and hc π + π − with no violation of the heavy quark spin. Since the Breit-Wigner
parameters of the peaks measured in the two channels χc0 ω and hc π + π − are very similar, we test the hypothesis that
the two observed structures may coincide.
We fit data with the same models (I and II in the following) considered in Refs. [1, 4]. In the hc π + π − invariant mass
distribution, we add to the BES dataset the experimental point σhc π+ π− (4.17 GeV) = (15.6 ± 4.2) pb1 by CLEO-c [8],
with statistical and systematic errors added in quadrature. For the BES data, we take into account only statistical
errors, since the systematic ones are common to all points and are not expected to modify the shape of the distribution.
Following model-I, we fit the hc π + π − and χc0 ω data with the sum of a Breit-Wigner and a pure phase-space
background. To test our hypothesis, the mass and the width of the resonance are constrained to be the same in both
channels. Thus, the fitting functions are:
2
Beiφ1
σhc π+ π− (m) = A + p
BW(m, m0 , Γ) PS3 (m),
PS3 (m0 )
2
Deiφ2
σχc0 ω (m) = C + p
BW(m, m0 , Γ) PS2 (m),
PS2 (m0 )
(1)
(2)
where m0 and Γ are the mass and width of the resonance, m is the invariant mass of the system, BW(m, m0 , Γ) =
−1
p
p
, B = 12πBhc π+ π− Γee Γ, D = 12πBχc0 ω Γee Γ, and PSn is the n-body phase space. With this
m2 − m20 + im0 Γ
model, we get a mass of 4214 ± 10 MeV and a width of 50 ± 21 MeV. The χ2 /DOF = 17.81/15, corresponding to a
Prob(χ2 ) = 27%.
To obtain the significance of the Y (4220), we perform a likelihood ratio test: we repeat the fit according to a pure
phase-space background hypothesis, i.e. forcing B = D = 0. The ∆χ2 /∆DOF with respect to the full fit is 131/6,
which rejects the pure background hypothesis with a significance > 10σ.
By comparing the Breit-Wigner amplitudes in the two channels, we get the ratio:
B (Y (4220) → χc0 ω)
= 8.5 ± 4.8 ± 1.9
B (Y (4220) → hc π + π − )
1
σf (m) indicates the cross section σ(e+ e− → f ) at
√
s = m.
(3)

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