11th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

Constraining the initial condition of the QGP using experimental observables is one of the most important challenges in our field. Recent studies show that the Pearson Correlation Coefficient (PCC) between $v_n$ and event-wise mean transverse momentum $[p_{\mathrm{T}}]$, ${\rho }_n(v_n,[p_{\mathrm{T}}])$, and $[p_{\mathrm{T}}]$ fluctuations can probe several ingredients of the initial state. This talk presents precision measurements of $v_n-[p_{\mathrm{T}}]$ correlation for n=2,3 and 4 and high order $[p_{\mathrm{T}}]$ fluctuations in ${}^{129}$Xe+${}^{129}$Xe and ${}^{208}$Pb+${}^{208}$Pb collisions, and they are found to be small in the mid-central and central collisions in these systems. The ${\rho }_n$ and variance and skewness of $[p_{\mathrm{T}}]$ fluctuations show non-monotonic dependence on centrality, $p_{\mathrm{T}}$ and $\eta$. It was also found that the result depends on the centrality estimator used in the analysis, indicating a strong influence of volume fluctuations. In central collisions, where models generally show good agreement, the $v_2$--$[p_{\mathrm{T}}]$ correlations are sensitive to the triaxiality of the quadrupole deformation. A comparison of the model with the Pb+Pb and Xe+Xe data confirms that the ${}^{129}$Xe nucleus is a highly deformed triaxial ellipsoid that has neither a prolate nor oblate shape. This provides strong evidence for a triaxial deformation of the ${}^{129}$Xe nucleus from high-energy heavy-ion collisions.