Measurements of identified particle anisotropic flow in Cu+Au and U+U collisions by PHENIX experiment

In this paper, new measurements of anisotropic flow ($v_1$, $v_2$) for identified particles such as pions and proton in Cu+Au collisions at 200 GeV and U+U collisions at 193 GeV are reported. The anisotropic flow is studied as a function of $p_T$ and centrality in these two collision systems. In ultra-central U+U collisions (0–2% centrality), $v_2$ of protons shows a weak $p_T$ dependence for $p_T<$~1.0 GeV/c. A positive $v_1$ for charged pions is observed for $p_T>$ 1 GeV/c with respect to the first-order event plane, the angle of which is determined by the Au-going spectators. The scaling of identified particles $v_2$ with the number of valence quarks ($n_q$) has been observed, in different centrality bins, with the transverse kinetic energy in these two collision systems.