Speaker
Description
Directed and elliptic flow ($v_1$ and $v_2$), are sensitive to the dynamics during the early stages of the system
evolution and equation of state of the medium.
The $v_1$ slope ($dv_1/dy$) at mid-rapidity of net-baryons is expected to be sensitive to the first-order phase transition, while the Number of Constituent Quark (NCQ) scaling of elliptic flow is regarded as a signal of formation of Quark-Gluon Plasma (QGP).
From the measurements based on the first phase of RHIC beam energy scan (BES-I), the $dv_1/dy$ of net-proton exhibits non-monotonous dependence on collision energy, with a minimum between 11.5 and 19.6 GeV.
The elliptic flow of identified particles at 3 GeV is negative and NCQ scaling is absent unlike at top RHIC energies.
Measurements at more energies within these regions would provide crucial insight into the stages of the medium evolution.
In this talk, the measurements of $v_1$ and $v_2$ for light and (multi-)strange particles at $\sqrt{s_{\rm{NN}}}$ = 3 - 19.6 GeV
from the second phase of the RHIC beam energy scan (BES-II) program will be presented.
The rapidity and transverse momentum ($p_T$) dependence of $v_1$ and $v_2$ will be shown. Also,
the centrality and energy dependence of $v_1$ slope, NCQ scaling, and $p_T$-integrated $v_2$ will be discussed.
The experimental results will be compared with model calculations.
Implications of these measurements on understanding of QCD phase structure will be discussed.
