Speaker
Description
Anisotropic flow coefficients $v_n$ have been used as a tool to probe the initial conditions and transport properties of the strongly interacting matter produced in heavy-ion collisions. In this talk we report on the measurements of $p_{\rm T}$-differential $v_2$ and $v_3$ coefficients for charged hadrons using two-and multi-particle cumulants in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV and Xe-Xe collisions at $\sqrt{s_{\rm NN}} = 5.44$ TeV. In order to discuss the non-flow effects, we also present results obtained using a novel 2-subevent technique. We observe that the $v_2\{6\}$ and $v_2\{8\}$ deviate from $v_2\{4\}$, indicating that the underlying probability density distribution of $v_n$ coefficients is not well-described by the Bessel-Gaussian distribution. This provides new constraints on the initial geometry and its event-by-event fluctuations of heavy-ion collisions. Moreover, the non-trivial evolution of $v_2\{6\}/v_2\{4\}$ and $v_2\{8\}/v_2\{4\}$ ratios with $p_{\rm T}$ suggests that the transport properties of the expanding medium play an important role to the azimuthal distributions of charged hadrons.
