Measurement of $v_n$ - mean $p_T$ correlations in lead-lead collisions at $\sqrt{s_{NN}} = 5.02$ TeV with the ATLAS detector.

The lead-lead data collected by the ATLAS detector at the LHC provide new opportunities to study dynamic properties of quark-gluon plasma. A tool to study these properties is the recently proposed modified Pearson's correlation coefficient, $\rho$, that quantifies the correlation between the mean transverse momentum in the event, $[p_T]$, and the square of the flow harmonic magnitude, $v_n^2$. The measurement of $\rho$ for $n$=2, 3 and 4 is performed using 22~$\mu \mathrm{b}^{-1}$ of minimum-bias Pb+Pb data at $\sqrt{s_{NN}}$ = 5.02 TeV collected with the ATLAS detector at the LHC. To suppress non-flow effects, $v_n^2$ is calculated by correlating charged particles from two sub-events covering opposite pseudorapidity ranges of 0.75 $< |\eta| <$ 2.5 while $[p_T]$ is evaluated for particles with $|\eta|<$ 0.5. Significant (non-zero) values of $\rho$ coefficients for all studied harmonics are obtained. The $\rho$ coefficient as a function of centrality is observed to weakly depend on the transverse momentum range of the selected particles, despite large differences in the mean event transverse momentum and the magnitude of flow harmonics fluctuations. The $\rho$ coefficient for the second order harmonic is found to be negative in peripheral events, have a significant positive value for mid-central events and to drop in the most central events. Measured coefficients are compared to theoretical models.