Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session R10: Minisymposium on Probing High Baryon Density Physics IIMiniSymposium

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Sponsoring Units: DNP Chair: Chun Shen, BNL Room: A216 
Monday, April 16, 2018 10:45AM  10:57AM 
R10.00001: Directed flow of particles and quarks from the RHIC Beam Energy Scan measured by STAR Prashanth Shanmuganathan The Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider aims to study the QCD phase diagram in a region where a critical point may exist. Possible signatures of a softening of the QCD equation of state have been reported at BES energies, and directed flow (rapidityodd $v_1(y)$) is has been measured by STAR indicating an intriguing double sign change behavior. This talk will focus on $v_1$ and its slope, $dv_1/dy$, near midrapidity for ten identified particles in Au+Au collisions at eight beam energies measured by the STAR experiment. The coalescence assumption is used to interpret $v_1$ versus beam energy of the constituent quarks, which explores the separate contributions from quarks produced in the collision, and transported from the colliding nuclei. Tests of a coalescence sum rule are carried out for net particles, and implications for transported quark $v_1$ are also discussed. We will also discuss the detector upgrades and expected improvements in $v_1$ measurements from phase II of the of the Beam Energy Scan program. [Preview Abstract] 
Monday, April 16, 2018 10:57AM  11:09AM 
R10.00002: Twoparticle correlations of identified hadrons in Au+Au collisions for the Beam Energy Scan program at RHIC Sedigheh Jowzaee Twoparticle correlation function is a powerful tool to study the dynamics of the heavyion collisions in both longitudinal and azimuthal directions. These correlations indicate the importance of various physical mechanisms, such as energy and momentum conservation, jet fragmentation, resonance decays and HBT correlation effects, collective flow, and are possibly related to a critical point in the phase diagram of nuclear matter. The STAR Collaboration presented twoparticle rapidity correlation function for the most central events and different trends were observed for protons and pions.\footnote{S. Jowzaee for the STAR Collaboration, \textbf{Nucl. Phys. A} 967 (2017) 792795} In this talk, we show a detailed analysis of the rapidity and angular correlations of likesign and unlikesign identified hadrons ($p, K$ and $\pi$) as a function of the centrality from the most central (05$\%$) to the peripheral (7080$\%$), and collision energy of gold nuclei in the range of 7.7 to 200$~\mathrm{GeV}$ in the Au$+$Au collisions. The experimental results are compared to those from the UrQMD model\footnote{S. A. Bass {\it et al.}, \textbf{Prog. Part. Nucl. Phys.} 41 (1998) 255369}. [Preview Abstract] 
Monday, April 16, 2018 11:09AM  11:21AM 
R10.00003: New Development on Modelling Fluctuations and Fragmentation in HeavyIon Collisions Hao Lin, Pawel Danielewicz While nuclear multifragmentation has been observed and studied experimentally for decades, conventional transport models for heavyion collisions, due to a lack of proper treatment of fluctuations, cannot probe the various exit channels corresponding to different fragmentation configurations. In view of this, we have developed a new model to take into account realistic fluctuations. The new model, motivated by the Brownian description of colliding particles, recasts the effects of twobody collisions in terms of onebody diffusion processes. A wide range of dynamical paths are sampled by solving Langevin equations in momentum space. It is the stochastic sampling of dynamical paths that leads to a greater spread of exit channels. Good agreement in comparisons of final rapidity distribution and transverse flow in the Au + Au reactions with other transport models under controlled conditions is achieved, confirming the validity of the model. Its potential for describing nuclear multifragmentation is demonstrated in the study of $^{112,124}Sn$ + $^{112,124}Sn$ at 50 MeV/u, and results are compared with those from the stochastic meanfield (SMF) and the antisymmetrized molecular dynamics models (AMD) models. [Preview Abstract] 
Monday, April 16, 2018 11:21AM  11:33AM 
R10.00004: Equation of state for QCD with a critical point from the 3D Ising Model Paolo Parotto Currently, one of the major investigations in heavy ion physics concerns the search for the QCD high temperature critical point associated with the chiral transition, which has stimulated tremendous effort from both theory and experiment. On the theory side, a major role in the analysis of experimental results is played by hydrodynamical simulations of heavy ion collisions, which need as an input an equation of state driving the evolution of the system. Current knowledge of the finitedensity QCD equation of state from first principles is limited to a Taylor expansion in the baryonic chemical potential around $\mu_B = 0$. By means of a scaling form for the equation of state of the 3D Ising model and a nonuniversal, parametrized map to QCD coordinates, we construct an equation of state matching state of the art first principle Lattice QCD calculations and including the correct critical behavior, which can be readily employed in hydrodynamical simulations of heavy ion collisions at finite density, covering most of the BES range at RHIC. The parametrized form of this equation of state can be exploited to constrain the value of the parameters themselves by imposing thermodynamic consistency and through comparison of predictions obtained by simulations with experimental results. [Preview Abstract] 
Monday, April 16, 2018 11:33AM  11:45AM 
R10.00005: (3+1)D hybrid model of heavyion collisions at BES energies with dynamical sources Lipei Du, Gojko Vujanovic, Ulrich Heinz At Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies, the dynamics of the preequilibrium stage and the effects resulting from a nonzero net baryon current become critical components of the dynamical evolution of the collision fireball. We develop a (3+1)dimensional hybrid evolution model with dynamical sources for both energymomentum and the net baryon current. During an initial preequilibrium stage based on UrQMD, the fourmomenta and baryon numbers carried by secondary particles created within UrQMD are fed continuously, after a short thermalization time, into a (3+1)dimensional viscous hydrodynamic evolution module. This initialization provides an alternate model to those recent studies [1, 2]: It thermalizes more rapidly than Ref. [1] and yields a different initial net baryon distribution than Ref. [2]. We present and compare with these previous approaches the dynamical evolution of all thermodynamic and dissipative degrees of freedom, including net baryon diffusion. The sensitivity of experimental observables (spectra and anisotropic flows) to the details of the preequilibrium stage and to baryon diffusion will also be demonstrated.\\{}[1] H. Petersen et al., Phys. Rev. C 78, 044901 (2008).\\{}[2] C. Shen and B. Schenke, arXiv:1710.00881 [nuclth]. [Preview Abstract] 
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