Mon·Apr 3, 2017Monday·April 3, 2017

1. 01*

   Measurement of the Shared Momentum Fraction $z_g$ using Jet Reconstruction in p+p and Au+Au Collisions with STAR

   Kolja Kauder (for the STAR Collaboration)🇺🇸

   One key difference in current energy loss models lies in the treatment of the Altarelli-Parisi, AP, splitting functions. It has been shown that the shared momentum fraction, henceforth called Jet Splitting Function $z_g$ as determined by the SoftDrop grooming process can be made a Sudakov-safe measurement of the symmetrized AP functions in p+p collisions. The STAR collaboration presents the first $z_g$ measurements at $\sqrt{s_{NN}}=200$ GeV in p+p and Au+Au collisions, where in Au+Au we use the specific di-jet selection introduced in our previous momentum imbalance measurement. For a jet resolution parameter of $R=0.4$, these di-jet pairs were found to be significantly imbalanced with respect to p+p, yet regained balance when all soft constituents were included. We find that within uncertainties there are no signs of a modified Jet Splitting Function on trigger or recoil side of this di-jet selection.

   nucl-exNucl.Part.Phys.Proc.(2017)·30 citations
2. 02*

   Onset of hydrodynamics for a quark-gluon plasma from the evolution of moments of distribution functions

   Jean-Paul Blaizot🇫🇷 · Li Yan🇨🇦

   The pre-equilibrium evolution of a quark-gluon plasma produced in a heavy-ion collision is studied in the framework of kinetic theory. We discuss the approach to local thermal equilibrium, and the onset of hydrodynamics, in terms of a particular set of moments of the distribution function. These moments quantify the momentum anisotropies to a finer degree than the commonly used ratio of longitudinal to transverse pressures. They are found to be in direct correspondence with viscous corrections of hydrodynamics, and provide therefore an alternative measure of these corrections in terms of the distortion of the momentum distribution. As an application, we study the evolution of these moments by solving the Boltzmann equation for a boost invariant expanding system, first analytically in the relaxation time approximation, and then numerically for a quark-gluon plasma within the small angle approximation to the collision kernel.

   ↳ nucl-thhep-phnucl-exJHEP(2017)·54 citations
3. 03*

   Collective flow in 2.76 A TeV and 5.02 A TeV Pb+Pb collisions

   Wenbin Zhao🇨🇳 · Hao-jie Xu🇨🇳 · Huichao Song (Peking U.)🇨🇳

   In this paper, we study and predict flow observables in 2.76 A TeV and 5.02 A TeV Pb +Pb collisions, using the iEBE-VISHNU hybrid model with TRENto and AMPT initial conditions and with different forms of the QGP transport coefficients. With properly chosen and tuned parameter sets, our model calculations can nicely describe various flow observables in 2.76 A TeV Pb +Pb collisions, as well as the measured flow harmonics of all charged hadrons in 5.02 A TeV Pb +Pb collisions. We also predict other flow observables, including $v_n(p_T)$ of identified particles, event-by-event $v_n$ distributions, event-plane correlations, (Normalized) Symmetric Cumulants, non-linear response coefficients and $p_T$-dependent factorization ratios, in 5.02 A TeV Pb+Pb collisions. We find many of these observables remain approximately the same values as the ones in 2.76 A TeV Pb+Pb collisions. Our theoretical studies and predictions could shed light to the experimental investigations in the near future.

   ↳ nucl-thhep-phnucl-exEPJC(2017)·126 citations
4. 04*

   Trace radioactive impurities in final construction materials for EXO-200

   D.S. Leonard🇰🇷 · D. Auty🇺🇸 · T. Didberidze🇺🇸 · R. Gornea🇨🇦 · P. Grinberg🇨🇦 · R. MacLellan🇺🇸 · B. Methven🇨🇦 · A. Piepke🇺🇸 · J.-L. Vuilleumier🇨🇭 · J.B. Albert🇺🇸 · G. Anton🇩🇪 · I. Badhrees🇨🇦 and 89 other authors

   We report results from a systematic measurement campaign conducted to identify low radioactivity materials for the construction of the EXO-200 double beta decay experiment. Partial results from this campaign have already been reported in a 2008 paper by the EXO collaboration. Here we release the remaining data, collected since 2007, to the public. The data reported were obtained using a variety of analytic techniques. The measurement sensitivities are among the best in the field. Construction of the EXO-200 detector has been concluded, and Phase-I data was taken from 2011 to 2014. The detector's extremely low background implicitly verifies the measurements and the analysis assumptions made during construction and reported in this paper.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2017)·37 citations
5. 05*

   Final state multiplicity and particle correlation in small systems

   Valentina Mariani🇮🇹

   Final state variables and particle correlation will be discussed under a Multiple Parton Interaction (MPI) interpretation. The state of the art about the latest results on such variables will be provided. Furthermore the role played by event multiplicity in the deep understanding of particle correlation, in particular concerning the new results on the Long-Range Near-Side two particle correlations by the CMS Collaboration, will be discussed.

   ↳ hep-exnucl-ex0 citations
6. 06*

   Nuclear dependence of the transverse-single-spin asymmetry for forward neutron production in polarized $p$$+$$A$ collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

   C. Aidala · Y. Akiba · M. Alfred · V. Andrieux · K. Aoki · N. Apadula · H. Asano · C. Ayuso · B. Azmoun · V. Babintsev · A. Bagoly · N.S. Bandara and 304 other authors

   During 2015 the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized $p$$+$$p$ collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in $p$$+$$p$ collisions predicts only a moderate atomic-mass-number ($A$) dependence. In contrast, the asymmetries observed at RHIC in $p$$+$$A$ collisions showed a surprisingly strong $A$ dependence in inclusive forward neutron production. The observed asymmetry in $p$$+$Al collisions is much smaller, while the asymmetry in $p$$+$Au collisions is a factor of three larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed $A$ dependence.

   ↳ hep-exnucl-exPRL(2018)·30 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.