Directed flow in Au+Au collisions from the RHIC Beam Energy Scan at the STAR experiment

الأصل · EN

We report results of v₁(y) and dv₁/dy near mid-rapidity for π±, K±, Kₛ⁰, p, p, Λ, Λ and ϕ from Beam Energy Scan Au+Au collisions at √sNN = 7.7 - 200 GeV using the STAR detector at RHIC. The dv₁/dy of π±, K± and Kₛ⁰ mesons remains negative over all beam energies. The dv₁/dy of p and Λ baryons shows a sign change around 10 - 15 GeV, while net baryons (net p and net Λ) indicate a double sign change. The dv₁/dy of p, Λ and ϕ show a similar trend for √sNN> 14.5 GeV. For the first time, v₁ measurements are used to test a quark coalescence hypothesis. Many measurements are found to be consistent with the particles being formed via coalescence of constituent quarks. The observed deviations from that consistency offer a new approach for probing the collision process at the quark level.