Correlations between harmonic flow and transverse momentum in pp and p+Pb collisions at the LHC with the ATLAS detector.

The study of the correlation between harmonic flow $v_n$ and mean transverse momentum $[p_T]$ in proton-proton collisions at $\sqrt{s} = 5.02$ and $13$ TeV and proton-lead at $\sqrt{s} = 5.02$ TeV with the ATLAS detector has been conducted. It is performed for charged particles with pseudorapidity range $|\eta|<2.5$ and various transverse momentum ranges. The measured observable is a modified form of Pearson's correlation coefficient ($\rho\left(v_n\{2\}^2,\, \left[p_T\right] \right)$) between flow $v_n\{2\}^2$ and $p_T$. The results are presented for harmonics $n$ = 2 and 3, and three arrangements of sub-events. The results for ${pp}$ are compared with Pythia which does not contain modeling of QGP. It would allow us to study the non-flow contribution to the observed correlation. The effects of QCD color reconnection parameters in Pythia on measured correlation are found to be significant to reproduce flow-like pattern. The Pythia reproduces qualitatively the same trend as data but fails in describing it quantitatively, indicating a missing physics in this generator. Comparison with EPOS, which includes hydrodynamic simulation, is also studied. The results for ${p}-Pb$ are compared to samples from HIJING in 1-subevent and IP-Glasma+MUSIC+UrQMD and 3+1D hydrodynamic with Glauber initial state.