Initial-state fluctuations from midperipheral to ultracentral collisions in an event-by-event transport approach

We have developed a relativistic kinetic transport approach that incorporates initial-state fluctuations allowing to study the buildup of elliptic flow v(2) and high-order harmonics v(3), v(4), and v(5) for a fluid at fixed eta/s(T). We study the effect of the eta/s ratio and its T dependence on the buildup of the v(n) (p(T)) for two different beam energies: RHIC for Au+Au at root s = 200 GeV and LHC for Pb + Pb at root s = 2.76 TeV. We find that for the two different beam energies considered the suppression of the v(n) (p(T)) due to the viscosity of the medium have different contributions coming from the crossover or QGP phase. Our study reveals that only in ultracentral collisions (0-0.2%) the v(n) (p(T)) have a stronger sensitivity to the T dependence of eta/s in the QGP phase and this sensitivity increases with the order of the harmonic n. Moreover, the study of the correlations between the initial spatial anisotropies epsilon(n) and the final flow coefficients v(n) shows that at LHC energies there is more correlation than at RHIC energies. The degree of correlation increases from peripheral to central collisions, but only in ultracentral collisions at LHC, we find that the linear correlation coefficient C(n, n) approximate to 1 for n = 2,3,4, and 5. This suggests that the final correlations in the (v(n), v(m)) space reflect the initial correlations in the (epsilon(n), epsilon(m)) space.