Speaker
Shusu Shi
Description
The Beam Energy Scan (BES) program at the RHIC facility was initiated in
the year 2010 to study the Quantum Chromodynamics (QCD) phase
diagram[1]. In the years 2010, 2012 and 2014 the STAR experiment
recorded Au + Au collisions at \sqrt{s_{NN}} = 7.7, 11.5, 14.5, 19.6,
27, 39, and 62.4 GeV within a pseudo rapidity range of |\eta|< 1.
Recently reported results from identified particle elliptic flow in
minimum bias (0–80%) collisions revealed an energy dependent
difference in elliptic flow between particles and antiparticles [2].
This difference is increasing with decreasing collision energy and is
almost identical for all baryons. These observations attracted various
theory groups, that tried to reproduce the results with different
assumptions in their model calculations [3].
In this talk, we present the elliptic flow of identified particle for
three centrality classes in Au + Au collisions at \sqrt{s_{NN}} = 7.7 -
62.4 GeV. The centrality dependence and the data at \sqrt{s_{NN}} = 14.5
GeV are new. Except at the lowest beam energies, we observe a similar
relative v2 baryon-meson splitting for all centrality classes which is
in agreement within 15% with the number-of-constituent quark scaling.
The larger v2 for most particles relative to antiparticles, already
observed for minimum bias collisions shows a clear centrality
dependence, with the largest difference in the most central collisions.
The new beam energy (14.5 GeV) and centrality dependence would be useful
to distinguish between the different models or to improve their input
parameters.
[1] M. M. Aggarwal et al. (STAR Collaboration), arXiv:1007.2613. [2] L.
Adamczyk et al. (STAR Collaboration), Phys. Rev. Lett. 110, 142301
(2013). [3] J. Steinheimer, V. Koch, and M. Bleicher, Phys. Rev. C 86,
044903 (2013); J. Xu, et al., Phys. Rev. Lett. 112, 012301 (2014).
| On behalf of collaboration: | STAR |
|---|
Author
Shusu Shi
