Speaker
Yadav Pandit
(For the STAR Collaboration)
Description
Measurements of anisotropic flow in heavy-ion collisions
provide insight into the early stage of the system's
evolution. Directed flow, $v_1$, is imparted especially
early. A change of sign in the slope of $dv_1/dy$ for
identified particles, particularly for protons, has been
suggested as a possible signal of a first-order phase
transition. In this talk, we present the STAR measurements
of $v_1$ for $\pi^\pm$, $K^\pm$, protons and antiprotons, as
well as for all detected charged particles in Au + Au
collisions at $\sqrt{s_{NN}}$ = 39, 11.5 and 7.7 GeV as a
function of transverse momentum, rapidity and centrality. At
$\sqrt{s_{NN}}$ = 39 GeV, all measured $v_1$ values follow
the trend observed at higher RHIC energies. At
$\sqrt{s_{NN}}$ = 11.5 and 7.7 GeV, the proton $dv_1/dy$ near
midrapidity changes sign between peripheral and central
collisions. This behavior is not observed for
antiprotons, $\pi^\pm$ and $K^\pm$. Results are compared to
available model predictions.
Primary author
Yadav Pandit
(For the STAR Collaboration)
