Probing the onset of hydrodynamization in peripheral p-Pb collisions at $\sqrt{s_{NN}} =$ 5.02 TeV

TL;DR

This study investigates the onset of hydrodynamic behavior in small p-Pb collision systems at 5.02 TeV by analyzing elliptic flow and transport coefficients, finding fluid behavior breaks down at low multiplicities.

Contribution

It introduces a detailed hydrodynamic modeling approach to estimate the minimum size for QGP formation in small systems, highlighting the sensitivity of elliptic flow to transport coefficients.

Findings

Hydrodynamic behavior breaks down at $dN/dy \, \approx \, 14$ in p-Pb collisions.

Elliptic flow fluctuations increase as system size decreases.

Comparison with experimental data supports the hydrodynamic modeling results.

Abstract

An attempt has been made to estimate the minimum size of the de-confined matter of Quark-Gluon Plasma (QGP) in small systems like p-Pb system that could be satisfactorily modeled with low-order hydrodynamics. The variation of second order transport coefficient of second order relativistic viscous hydrodynamics, the shear relaxation time has been utilized to study the sensitivity of experimental observables like elliptic flow coefficient. A representative system of p-Pb collisions at $\sqrt{s_{NN}} =$ 5.02 TeV, simulated with the state-of-art framework of JETSCAPE event generator was used to study the variation of elliptic flow coefficient for peripheral collisions. The soft sector dynamics was simulated using an initial condition, a pre-equilibrium stage, hydrodynamics and a hadron afterburner. The transverse momentum spectra and rapidity distribution was obtained for light flavored hadrons and compared with the experimental data. The increase in elliptic flow fluctuations indicate breakdown of fluid behavior at $dN/dy \approx 14$ for p-Pb collision at $\sqrt{s_{NN}} =$ 5.02 TeV.