Inclusive charged hadron elliptic flow in Au + Au collisions at √sNN = 7.7 - 39 GeV

الأصل · EN

A systematic study is presented for centrality, transverse momentum (pₜ) and pseudorapidity (η) dependence of the inclusive charged hadron elliptic flow (v₂) at midrapidity(|η| < 1.0) in Au+Au collisions at √sNN = 7.7, 11.5, 19.6, 27 and 39 GeV. The results obtained with different methods, including correlations with the event plane reconstructed in a region separated by a large pseudorapidity gap and 4-particle cumulants (v₂4), are presented in order to investigate non-flow correlations and v₂ fluctuations. We observe that the difference between v₂2 and v₂4 is smaller at the lower collision energies. Values of v₂, scaled by the initial coordinate space eccentricity, v₂/ε, as a function of pₜ are larger in more central collisions, suggesting stronger collective flow develops in more central collisions, similar to the results at higher collision energies. These results are compared to measurements at higher energies at the Relativistic Heavy Ion Collider (√sNN = 62.4 and 200 GeV) and at the Large Hadron Collider (Pb + Pb collisions at √sNN = 2.76 TeV). The v₂(pₜ) values for fixed pₜ rise with increasing collision energy within the pₜ range studied (< 2 GeV/c). A comparison to viscous hydrodynamic simulations is made to potentially help understand the energy dependence of v₂(pₜ). We also compare the v₂ results to UrQMD and AMPT transport model calculations, and physics implications on the dominance of partonic versus hadronic phases in the system created at Beam Energy Scan (BES) energies are discussed.