Directed flow of quarks from the RHIC Beam Energy Scan measured by STAR

Journal Article · Tue Jan 22 00:00:00 EST 2019 · Nuclear Physics. A

DOI:https://doi.org/10.1016/j.nuclphysa.2018.08.036· OSTI ID:1580363

Wang, Gang  ^[1]

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1. Univ. of California, Los Angeles, CA (United States)

Directed flow (ν₁) is a good probe of the early-stage dynamics of collision systems, and the ν₁ slope at midrapidity (dv₁/dy|_y=0) is sensitive to the system's equation of state. STAR has published ν₁(y) measurements for ten particle species (π^±,$$p, \bar{p},Λ,\bar{Λ},ϕ,K^± and K_S^0$$) in Au+Au collisions at eight beam energies from $$ \sqrt{s_{NN}}$$ = 7.7 GeV to 200 GeV. In this study, we employ a simple coalescence idea to decompose ν₁ of hadrons into ν₁ of constituent quarks. The dv₁/dy values of $$\bar{p},\bar{K},$$ and $$\bar{Λ}$$ are used to test the coalescence sum rule for produced quarks. Data involving produced quarks support the coalescence picture at $$ \sqrt{s_{NN}}$$ =11.5 GeV to 200 GeV, and a sharp deviation from this picture is observed at 7.7 GeV. The dv₁/dy of transported quarks is studied via net particles (net p and net Λ). In these proceedings, we further extract the ν₁ slopes of produced and transported quarks, assuming that the coalescence sum rule is valid.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: STAR Collaboration
• DOE Contract Number: AC02-05CH11231; FG02-88ER40424
• OSTI ID: 1580363
• Journal Information: Nuclear Physics. A, Vol. 982, Issue C; ISSN 0375-9474
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
heavy-ion collision
directed flow
beam energy scan
coalescence
transported quark