Wenbin Zhao, Weiyao Ke, Wei Chen, Tan Luo, and Xin-Nian Wang, From Hydrodynamics to Jet Quenching, Coalescence, and Hadron Cascade: A Coupled Approach to Solving the RAA⊗v2 Puzzle, Phys. Rev. Lett. 128, 022302 (2022)

Hydrodynamics and jet quenching are responsible for the elliptic flow v2 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 RAA and v2, especially at intermediate pT, however, remains a challenge. We solve this long-standing RAA⊗v2 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 v2 for pions, kaons, and protons in the intermediate pT region. We demonstrate for the first time that experimental data on R_AA , v₂, 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.

Upper Figure: The nuclear modification factor  R_AA of charged hadrons as compared to ALICE experimental data from the LHC.

Lower Figure: Anisotropy v₂ compared to the experimental data.