From hydro to jet quenching, coalescence and hadron cascade: a coupled approach to solving the $R_{AA}\otimes v_2$ puzzle

TL;DR

This paper presents a coupled hydrodynamic and transport model that successfully explains the simultaneous behavior of hadron suppression and elliptic flow in high-energy heavy-ion collisions, resolving a long-standing puzzle.

Contribution

It introduces a novel coupled linear Boltzmann transport-hydro model incorporating quark coalescence and hadron cascade to simultaneously describe $R_{AA}$ and $v_2$ across a wide $p_T$ range.

Findings

Reproduces experimental $R_{AA}$ and $v_2$ data from low to high $p_T$

Demonstrates flavor-dependent splitting of $v_2$ for different hadrons

Provides a unified framework for understanding QGP phenomena

Abstract

Hydrodynamics and jet quenching are responsible for the elliptic flow $v_2$ and suppression of large transverse momentum ($p_T$) hadrons, respectively, two of the most important phenomena leading to the discovery of a strongly coupled quark-gluon plasma (QGP) in high-energy heavy-ion collisions. A consistent description of the hadron suppression factor $R_{AA}$ and $v_2$, especially at intermediate $p_T$, however, remains a challenge. We solve this long-standing $R_{AA}\otimes v_2$ puzzle by including quark coalescence for hadronization and final state hadron cascade in the coupled linear Boltzmann transport-hydro model that combines concurrent jet transport and hydrodynamic evolution of the bulk medium. We illustrate that quark coalescence and hadron cascade, two keys to solving the puzzle, also lead to a splitting of $v_2$ for pions, kaons and protons in the intermediate $p_T$ region. We demonstrate for the first time that experimental data on $R_{AA}$, $v_2$ and their hadron flavor dependence from low to intermediate and high $p_T$ in high-energy heavy-ion collisions can be understood within this coupled framework.