From Hydrodynamics to Jet Quenching, Coalescence, and Hadron Cascade: A Coupled Approach to Solving the R_{AA}⊗v_{2} Puzzle.

Wenbin Zhao,Weiyao Ke,Tan Luo,Wei Chen,Xin-Nian Wang

doi:10.1103/physrevlett.128.022302

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 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}⊗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.

Highlights

From Hydrodynamics to Jet Quenching, Coalescence, and Hadron Cascade: A Coupled Approach to Solving the RAA ⊗ v2 Puzzle
Hydrodynamics and jet quenching are responsible for the elliptic flow v2 and suppression of large transverse momentum hadrons, respectively, two of the most important phenomena leading to the discovery of a strongly coupled quark-gluon plasma in high-energy heavy-ion collisions
Introduction.—Experimental evidences at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) have confirmed the existence of a strongly coupled quark-gluon plasma (QGP) in high-energy heavy-ion (A þ A) collisions [1,2,3,4,5]

Summary

Published by the American Physical Society

Describe hadron production from low to intermediate and high pT in high-energy heavy-ion collisions. We carry out a first study that couples event-by-event hydrodynamics, jet quenching, quark coalescence, and hadron cascade We demonstrate that this fully coupled approach can simultaneously describe RAA, differential v2, and their NCQ dependence in the full range of pT in high-energy heavy-ion collisions, solving the long-standing RAA ⊗ v2 puzzle that connects the two most important aspects of the discovery of a strongly coupled QGP. The interplay between hadron freeze-out in hydro and parton dynamics is defined by a separation scale pTs 1⁄4 1.5 GeV=c for the effective constituent quarks, above which viscous corrections to the equilibrium distribution become large and parton coalescence and fragmentation become the relevant mechanisms for hadronization. 40%–50% and (b) Pb þ Pb collisions aitdepnffistffiiffiNfffiffiiNffieffiffi d1⁄4π5, .0K2, and TeV p (solid) in 40%–50% and contributions from hydro freeze-out (dashed), parton coalescence (dot-dashed), and fragmentation (dotted) in COLBT-hydro simulations as compared to ALICE experimental data [112,113]

COLBT without πCoalescence

Pb þ Pb collisions at