Mon·Dec 14, 2015Monday·December 14, 2015

1. 01*

   First Results from The GlueX Experiment

   The GlueX Collaboration · H. Al Ghoul · E.G. Anassontzis · F. Barbosa · A. Barnes · T.D. Beattie · D.W. Bennett · V.V. Berdnikov · T. Black · W. Boeglin · W.K. Brooks · B. Cannon and 99 other authors

   The GlueX experiment at Jefferson Lab ran with its first commissioning beam in late 2014 and the spring of 2015. Data were collected on both plastic and liquid hydrogen targets, and much of the detector has been commissioned. All of the detector systems are now performing at or near design specifications and events are being fully reconstructed, including exclusive production of ${\pi }^0$, $\eta$ and $\omega$ mesons. Linearly-polarized photons were successfully produced through coherent bremsstrahlung and polarization transfer to the $\rho$ has been observed.

   nucl-exhep-exphysics.ins-detAIP Conf.Proc.(2016)·87 citations
2. 02*

   The antineutrino energy structure in reactor experiments

   P. Novella🇪🇸

   The recent observation of an energy structure in the reactor antineutrino spectrum is reviewed. The reactor experiments Daya Bay, Double Chooz and RENO have reported a consistent excess of antineutrinos deviating from the flux predictions, with a local significance of about 4$\sigma$ between 4 and 6 MeV of the positron energy spectrum. The possible causes of the structure are analyzed in this work, along with the different experimental approaches developed to identify its origin. Considering the available data and results from the three experiments, the most likely explanation concerns the reactor flux predictions and the associated uncertainties. Therefore, the different current models are described and compared. The possible sources of incompleteness or inaccuracy of such models are discussed, as well as the experimental data required to improve their precision.

   ↳ hep-exnucl-exphysics.ins-detAdv.High Energy Phys.(2015)·13 citations
3. 03*

   Nucleon Effective E-Mass in Neutron-Rich Matter from the Migdal-Luttinger Jump

   Bao-Jun Cai🇺🇸 · Bao-An Li🇺🇸

   The well-known Migdal-Luttinger theorem states that the jump of the single-nucleon momentum distribution at the Fermi surface is equal to the inverse of the nucleon effective E-mass. Recent experiments studying short-range correlations (SRC) in nuclei using electron-nucleus scatterings at the Jefferson National Laboratory (JLAB) together with model calculations constrained significantly the Migdal-Luttinger jump at saturation density of nuclear matter. We show that the corresponding nucleon effective E-mass is consequently constrained to $M_0^{\ast ,\mathrm{E}}/M\approx 2.22\pm 0.35$ in symmetric nuclear matter (SNM) and the E-mass of neutrons is smaller than that of protons in neutron-rich matter. Moreover, the average depletion of the nucleon Fermi sea increases (decreases) approximately linearly with the isospin asymmetry $\delta$ according to ${\kappa }_{\mathrm{p}/\mathrm{n}}\approx 0.21\pm 0.06\pm (0.19\pm 0.08)\delta$ for protons (neutrons). These results will help improve our knowledge about the space-time non-locality of the single-nucleon potential in neutron-rich nucleonic matter useful in both nuclear physics and astrophysics.

   ↳ nucl-thastro-ph.SRnucl-exPLB(2016)·9 citations
4. 04*

   Event-by-Event Identified Particle Ratio Fluctuations in Pb-Pb Collisions with ALICE using the Identity Method

   Mesut Arslandok (for the ALICE Collaboration)🇩🇪

   The study of event-by-event fluctuations of identified hadrons may reveal the degrees of freedom of the strongly interacting matter created in heavy-ion collisions and the underlying dynamics of the system. The observable ${\nu }_{dyn}$, which is defined in terms of the moments of identified-particle multiplicity distributions, is used to quantify the magnitude of the dynamical fluctuations in event-by-event measurements of particle ratios. The ALICE detector at the LHC is well-suited for the study of ${\nu }_{dyn}$, due to its excellent particle identification capabilities. Particle identification based on the measurement of the specific ionisation energy loss, d$E$/d$x$, works well on a statistical basis but suffers from ambiguities when applied on an event-by-event level. A novel experimental technique called the "Identity Method" is used to overcome such limitations. The first results on identified particle ratio fluctuations in Pb-Pb collisions at $\sqrt{s_{NN}}$=2.76TeV in ALICE as a function of centrality are presented. The ALICE results for the most peripheral events indicate an increasing correlation between pions and protons which is not reproduced by the HIJING and AMPT models. On the other hand, for the most central events the ALICE results agree with the extrapolations based on the data at lower energies from CERN-SPS and RHIC.

   ↳ hep-exnucl-exNPA(2016)·14 citations
5. 05*

   Comparing the Tsallis distribution with and without thermodynamical description in p+p collisions

   H. Zheng🇮🇹 · Lilin Zhu🇨🇳

   We compare two types of Tsallis distribution, i.e., with and without thermodynamical description, using the experimental data from the STAR, PHENIX, ALICE and CMS Collaborations on the rapidity and energy dependence of the transverse momentum spectra in p+p collisions. Both of them can give us the similar fitting power to the particle spectra. We show that the Tsallis distribution with thermodynamical description gives lower temperatures than the ones without it. The extra factor $m_T$ (transverse mass) in the Tsallis distribution with thermodynamical description plays an important role in the discrepancies between the two types of Tsallis distribution. But for the heavy particles, the choice to use the $m_T$ or $E_T$ (transverse energy) in the Tsallis distribution becomes more crucial.

   ↳ nucl-thnucl-exAdv.High Energy Phys.(2016)·90 citations
6. 06*

   LHCb results from proton ion collisions

   Laure Massacrier (on behalf of the LHCb Collaboration)🇫🇷

   Proton-lead and lead-proton data taking during 2013 has allowed LHCb to expand its physics program to heavy ion physics. Results include the first forward measurement of Z production in proton-lead collisions as well as a measurement of the nuclear modification factor and forward-backward production of prompt and displaced J/$\psi$, $\psi$(2S) and ${\rm Y}$. Angular particle correlations have also been measured for events of varying charged particle activity.

   ↳ hep-exnucl-exEPJ Web Conf.(2016)·0 citations
7. 07*

   Strangeness At Extremes

   Laura Tolos🇩🇪 · Daniel Cabrera🇩🇪 · Kanchan Khemchandani🇧🇷 · Alberto Martinez-Torres🇧🇷 · Elena Bratkovskaya🇩🇪 · Joerg Aichelin🇫🇷 · Marina Nielsen🇧🇷 · Fernando S. Navarra🇧🇷

   We study the properties of strange mesons in vacuum and in the hot nuclear medium within unitarized coupled-channel effective theories. We determine transition probabilities, cross sections and scattering lengths for strange mesons. These scattering observables are of fundamental importance for understanding the dynamics of strangeness production and propagation in heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exJPS Conf.Proc.(2017)·0 citations
8. 08*

   Low-Mass Dielectron Production in pp, p-Pb and Pb-Pb Collisions with ALICE

   Patrick Reichelt (for the ALICE Collaboration)🇩🇪

   The ALICE Collaboration measures the production of low-mass dielectrons in pp, p-Pb and Pb-Pb collisions at the LHC. The main detectors used in the analyses are the Inner Tracking System, Time Projection Chamber and Time-Of-Flight detector, all located at mid-rapidity. The dielectron yield in p-Pb collisions shows an overall agreement with the hadronic cocktail. The pair transverse momentum distributions are sensitive to the contributions from open heavy-flavours. In Pb-Pb collisions, uncorrected background-subtracted yields have been extracted in two centrality classes. In pp collisions the production of virtual photons relative to the inclusive yield is determined by analyzing the dielectron excess with respect to the expected hadronic sources. The direct photon cross section is then calculated and found to be in agreement with NLO pQCD calculations. A feasibility study for LHC Run 3 after the ALICE upgrade indicates the possibility for a future measurement of the early effective temperature.

   ↳ hep-exnucl-exNPA(2016)·2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.