Thu·Sep 24, 2015Thursday·September 24, 2015

1. 01*

   Transverse energy production and charged-particle multiplicity at midrapidity in various systems from $\sqrt{s_{NN}}=7.7$ to 200 GeV

   A. Adare🇺🇸 · S. Afanasiev🇷🇺 · C. Aidala🇺🇸 · N.N. Ajitanand🇺🇸 · Y. Akiba🇯🇵 · R. Akimoto🇯🇵 · H. Al-Bataineh🇺🇸 · J. Alexander🇺🇸 · M. Alfred🇺🇸 · A. Al-Jamel🇺🇸 · H. Al-Ta'ani🇺🇸 · A. Angerami🇺🇸 and 694 other authors

   Measurements of midrapidity charged particle multiplicity distributions, $d{N}_{\mathrm{ch}}/d\eta$, and midrapidity transverse-energy distributions, $d{E}_T/d\eta$, are presented for a variety of collision systems and energies. Included are distributions for Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$, 130, 62.4, 39, 27, 19.6, 14.5, and 7.7 GeV, Cu$+$Cu collisions at $\sqrt{s_{{}_{NN}}}=200$ and 62.4 GeV, Cu$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV, U$+$U collisions at $\sqrt{s_{{}_{NN}}}=193$ GeV, $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV, ${}^3$He$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV, and $p$$+$$p$ collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV. Centrality-dependent distributions at midrapidity are presented in terms of the number of nucleon participants, $N_{\mathrm{part}}$, and the number of constituent quark participants, $N_{q\mathrm{p}}$. For all $A$$+$$A$ collisions down to $\sqrt{s_{{}_{NN}}}=7.7$ GeV, it is observed that the midrapidity data are better described by scaling with $N_{q\mathrm{p}}$ than scaling with $N_{\mathrm{part}}$. Also presented are estimates of the Bjorken energy density, ${\epsilon }_{\mathrm{BJ}}$, and the ratio of $d{E}_T/d\eta$ to $d{N}_{\mathrm{ch}}/d\eta$, the latter of which is seen to be constant as a function of centrality for all systems.

   nucl-exPRC(2016)·169 citations
2. 02*

   Scaling properties of fractional momentum loss of high-pT hadrons in nucleus-nucleus collisions at $\sqrt{s_{{}_{NN}}}$ from 62.4 GeV to 2.76 TeV

   A. Adare · S. Afanasiev · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · H. Al-Bataineh · J. Alexander · M. Alfred · H. Al-Ta'ani · A. Angerami · K. Aoki and 619 other authors

   Measurements of the fractional momentum loss ($S_{\mathrm{loss}}\equiv \delta p_T/p_T$) of high-transverse-momentum-identified hadrons in heavy ion collisions are presented. Using ${\pi }^0$ in Au$+$Au and Cu$+$Cu collisions at $\sqrt{s_{{}_{NN}}}=62.4$ and 200 GeV measured by the PHENIX experiment at the Relativistic Heavy Ion Collider and and charged hadrons in Pb$+$Pb collisions measured by the ALICE experiment at the Large Hadron Collider, we studied the scaling properties of $S_{\mathrm{loss}}$ as a function of a number of variables: the number of participants, $N_{\mathrm{part}}$, the number of quark participants, $N_{\mathrm{qp}}$, the charged-particle density, $d{N}_{\mathrm{ch}}/d\eta$, and the Bjorken energy density times the equilibration time, ${\epsilon }_{\mathrm{Bj}}{\tau }_0$. We find that the $p_T$ where $S_{\mathrm{loss}}$ has its maximum, varies both with centrality and collision energy. Above the maximum, $S_{\mathrm{loss}}$ tends to follow a power-law function with all four scaling variables. The data at $\sqrt{s_{{}_{NN}}}$=200 GeV and 2.76 TeV, for sufficiently high particle densities, have a common scaling of $S_{\mathrm{loss}}$ with $d{N}_{\mathrm{ch}}/d\eta$ and ${\epsilon }_{\mathrm{Bj}}{\tau }_0$, lending insight on the physics of parton energy loss.

   nucl-exPRC(2016)·30 citations
3. 03*

   Transverse momentum dependence of D-meson production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   The production of prompt charmed mesons D${}^0$, D${}^{+}$ and D${}^{\ast +}$, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the centre-of-mass energy per nucleon pair, $\sqrt{s_{\mathrm{NN}}}$, of 2.76 TeV. The production yields for rapidity $|y|<0.5$ are presented as a function of transverse momentum, $p_{\mathrm{T}}$, in the interval 1-36 GeV/$c$ for the centrality class 0-10% and in the interval 1-16 GeV/$c$ for the centrality class 30-50%. The nuclear modification factor $R_{\mathrm{AA}}$ was computed using a proton-proton reference at $\sqrt{s}=2.76$ TeV, based on measurements at $\sqrt{s}=7$ TeV and on theoretical calculations. A maximum suppression by a factor of 5-6 with respect to binary-scaled pp yields is observed for the most central collisions at $p_{\mathrm{T}}$ of about 10 GeV/$c$. A suppression by a factor of about 2-3 persists at the highest $p_{\mathrm{T}}$ covered by the measurements. At low $p_{\mathrm{T}}$ (1-3 GeV/$c$), the $R_{\mathrm{AA}}$ has large uncertainties that span the range 0.35 (factor of about 3 suppression) to 1 (no suppression). In all $p_{\mathrm{T}}$ intervals, the $R_{\mathrm{AA}}$ is larger in the 30-50% centrality class compared to central collisions. The D-meson $R_{\mathrm{AA}}$ is also compared with that of charged pions and, at large $p_{\mathrm{T}}$, charged hadrons, and with model calculations.

   nucl-exhep-exJHEP(2016)·271 citations
4. 04*

   Forward-central two-particle correlations in p--Pb collisions with ALICE at the LHC

   Saehanseul Oh (for the ALICE Collaboration)🇺🇸

   We present the results of measurements of two-particle angular correlations between trigger particles reconstructed in the ALICE Forward Muon Spectrometer ($-4.0<\eta <-2.5$) and associated particles reconstructed in the central barrel detectors ($|\eta |<1.0$) in p--Pb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. At low transverse momentum ($p_{\mathrm{T}}$), the reconstructed trigger particles mainly originate from weak decays of primary pions and kaons, whereas at high $p_{\mathrm{T}}$, they originate mainly from the decay of heavy-flavor particles. The ridge structure elongated in the $\eta$-direction, discovered recently in p--Pb collisions, is found to persist to the pseudorapidity ranges studied here. The second-order Fourier coefficients of muons are extracted after subtracting the correlations obtained in low-multiplicity events from those in high-multiplicity events. The ratio of coefficients in the Pb-going and p-going directions is presented as a function of $p_{\mathrm{T}}$, and the coefficients are observed to have a similar $p_{\mathrm{T}}$ dependence in both directions with the Pb-going coefficients larger by 16$\pm$6\%. The results are compared with calculations from a multi-phase transport model.

   nucl-exhep-exNucl.Part.Phys.Proc.(2016)·0 citations
5. 05*

   The production of photons in relativistic heavy-ion collisions

   Jean-François Paquet🇨🇦 · Chun Shen🇨🇦 · Gabriel S. Denicol🇨🇦 · Matthew Luzum🇧🇷 · Björn Schenke🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   In this work it is shown that the use of a hydrodynamical model of heavy ion collisions which incorporates recent developments, together with updated photon emission rates greatly improves agreement with both ALICE and PHENIX measurements of direct photons, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy. The event-by-event hydrodynamical model uses IP-Glasma initial states and includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. The effect of both shear and bulk viscosities on the photon rates is studied, and those transport coefficients are shown to have measurable consequences on the photon momentum anisotropy.

   ↳ hep-phnucl-exnucl-thPRC(2016)·442 citations
6. 06*

   J/{\Psi} and {\Psi}(2S) Production in p-Pb Collisions at 5.02 TeV with ATLAS

   W. K. Brooks (ATLAS Collaboration)🇨🇱

   The production rates of heavy quarkonia in ion-ion collisions provide sensitive probes in the studies of the hot and dense matter formed in these collisions at high energies. However, a reference for understanding the behavior in the hot medium is necessary; p-A collisions open the possibility to study heavy quarkonia states in a smaller system of much lower average temperature. This is an important step in forming a baseline for understanding A-A collisions, as well as an investigation into the nature of modifications of the parton distributions in the nucleus. Using data collected at the LHC in 2013, we show results on the prompt J/{\Psi} and {\Psi}(2S) nuclear modification factors and the double ratio, {\Psi}(2S) divided by J/{\Psi} in p-Pb divided by the same in p-p, in p-Pb collisions at 5.02 TeV. The charmonia states were reconstructed via the dimuon decay channel and the yield is analyzed differentially in bins of transverse momentum, rapidity, and event activity.

   ↳ hep-exnucl-exNucl.Part.Phys.Proc.(2016)·3 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.