Wed·Jan 6, 2016Wednesday·January 6, 2016

1. 01*

   Nuclear Modification Factor of $D^0$ Meson in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV

   Guannan Xie (STAR collaboration)🇨🇳

   Heavy-flavor quarks are dominantly produced in initial hard scattering processes and experience the whole evolution of the system in heavy-ion collisions at RHIC energies. Thus they are suggested to be an excellent probe to the medium properties through their interaction with the medium. In this proceedings, we report our first measurement of $D^0$ production via topological reconstruction using STAR's recently installed Heavy Flavor Tracker (HFT). We also report our new measurement of Nuclear Modification Factor ($R_{AA}$) of $D^0$ mesons in central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV as a function of transverse momentum ($p_T$). New results confirm the strong suppression at high $p_T$ with a much improved precision, and show that the $R_{AA}$ at high $p_T$ are comparable with light hadrons ($\pi$) and with D meson measurements at the LHC. Furthermore, several theoretical calculations are compared to our data, and with charm diffusion coefficient 2$\pi T{D}_S$ $\sim$ 2-12 can reproduce both the $D^0$ $R_{AA}$ and $v_2$ data in Au+Au collisions at RHIC.

   nucl-exhep-exNPA(2016)·28 citations
2. 02*

   Transverse Energy Measurements from the Beam Energy Scan in PHENIX

   J.T. Mitchell (PHENIX Collaboration)🇺🇸

   Transverse energy distributions at midrapidity have been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) for Au+Au, U+U, Cu+Au, Cu+Cu, He+Au, d+Au, and p+p collisions over a wide energy range from $\sqrt{s_{NN}}$ = 7.7 GeV to $\sqrt{s_{NN}}$ = 200 GeV as a function of centrality. For central Au+Au collisions, it is observed that the midrapidity Bjorken energy density demonstrates a power law behavior from $\sqrt{s_{NN}}$ = 7.7 GeV to $\sqrt{s_{NN}}$ = 2.76 TeV. At a given collision energy, the data presented as a function of $N_{part}$ are independent of the size of the collision system. For Au+Au, Cu+Au, and Cu+Cu collisions, the centrality-dependent data are better described by scaling with the number of constituent quark participants than scaling with the number of nucleon participants.

   nucl-exNPA(2016)·7 citations
3. 03*

   Measurement of D-meson azimuthal anisotropy in Au+Au 200 GeV collisions at RHIC

   Michael R. Lomnitz (STAR collaboration)🇺🇸

   Heavy quarks are produced through initial hard scatterings and they are affected by the hot and dense medium created in heavy-ion collisions throughout its whole evolution. Due to their heavy mass, charm quarks are expected to thermalize much more slowly than light flavor quarks. The charm quark flow is a unique tool to study the extent of thermalization of the bulk medium dominated by light quarks and gluons. At high $p_T$, D meson azimuthal anisotropy is sensitive to the path length dependence of charm quark energy loss in the medium, which offers new insights into heavy quark energy loss mechanisms - gluon radiation vs. collisional processes. We present the STAR measurement of elliptic flow ($v_2$) of $D^0$ and $D^{\pm }$ mesons in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, for a wide transverse momentum range. These results are obtained from the data taken in the first year of physics running of the new STAR Heavy Flavor Tracker detector, which greatly improves open heavy flavor hadron measurements by the topological reconstruction of secondary decay vertices. The D meson $v_2$ is finite for $p_T>2{\text{ GeV/c}}^2$ and systematically below the measurement of light particle species at the same energy. Comparison to a series of model calculations favors scenarios where charm flows with the medium and is used to infer a range for the charm diffusion coefficient $2\pi T{D}_s$.

   ↳ hep-exnucl-exNPA(2016)·16 citations
4. 04*

   Effects of EoS in viscous hydro+cascade model for the RHIC Beam Energy Scan

   Iu. Karpenko🇺🇦 · M. Bleicher🇩🇪 · P. Huovinen🇩🇪 · H. Petersen🇩🇪

   A state-of-the-art 3+1 dimensional cascade + viscous hydro + cascade model vHLLE+UrQMD has been applied to heavy ion collisions in RHIC Beam Energy Scan range $\sqrt{s_{\mathrm{NN}}}=7.7\dots 200$ GeV. Based on comparison to available experimental data it was estimated that an effective value of shear viscosity over entropy density ratio $\eta /s$ in hydrodynamic stage has to decrease from $\eta /s=0.2$ to $0.08$ as collision energy increases from $\sqrt{s_{\mathrm{NN}}}=7.7$ to $39$ GeV, and to stay at $\eta /s=0.08$ for $39\le \sqrt{s_{\mathrm{NN}}}\le 200$ GeV. In this work we show how an equation of state with first order phase transition affects the hydrodynamic evolution at those collision energies and changes the results of the model as compared to "default scenario" with a crossover type EoS from chiral model.

   ↳ nucl-thhep-phnucl-exNPA(2016)·7 citations
5. 05*

   Anisotropic parton escape is the dominant source of azimuthal anisotropy in transport models

   Liang He · Terrence Edmonds · Zi-Wei Lin · Feng Liu · Denes Molnar · Fuqiang Wang

   We trace the development of elliptic anisotropy (v2) via parton-parton collision history in two transport models. The parton v2 is studied as a function of the number of collisions of each parton in Au+Au and d+Au collisions at sNN =200 GeV. It is found that the majority of v2 comes from the anisotropic escape probability of partons, with no fundamental difference at low and high transverse momenta. The contribution to v2 from hydrodynamic-type collective flow is found to be small. Only when the parton-parton cross-section is set unrealistically large does this contribution start to take over. Our findings challenge the current paradigm emerged from hydrodynamic comparisons to anisotropy data.

   ↳ nucl-thnucl-exPhysics Letters B (2016), pp. 506-510
6. 06*

   Charge-dependent correlations from event-by-event anomalous hydrodynamics

   Yuji Hirono🇺🇸 · Tetsufumi Hirano🇯🇵 · Dmitri E. Kharzeev🇺🇸

   We report on our recent attempt of quantitative modeling of the Chiral Magnetic Effect (CME) in heavy-ion collisions. We perform 3+1 dimensional anomalous hydrodynamic simulations on an event-by-event basis, with constitutive equations that contain the anomaly-induced effects. We also develop a model of the initial condition for the axial charge density that captures the statistical nature of random chirality imbalances created by the color flux tubes. Basing on the event-by-event hydrodynamic simulations for hundreds of thousands of collisions, we calculate the correlation functions that are measured in experiments, and discuss how the anomalous transport affects these observables.

   ↳ hep-phnucl-exnucl-thNPA(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.