Z+jet correlation with NLO-matched parton-shower and jet-medium interaction in high-energy nuclear collisions

Abstract

The impact of jet quenching on $Z^0$-tagged jets in relativistic heavy-ion collisions at the Large Hadron Collider (LHC) is investigated. We employ Sharpa Monte Carlo program that combines next-to-leading order matrix elements with matched resummation of parton shower to compute the initial $Z^0$+jet production. The Linear Boltzmann Transport (LBT) model is then used to simulate the propagation, energy attenuation of and medium response induced by jet partons in the quark-gluon plasma. With both higher-order corrections and matched soft/collinear radiation as well as a sophisticated treatment of parton energy loss and medium response in LBT, our numerical calculations can provide the best description so far of all available observables of $Z^0$+jet simultaneously in both p+p and Pb+Pb collisions, in particular, the shift of the distribution in transverse momentum asymmetry $x_{\rm jZ}=p_T^{\rm jet}/p_T^Z$, the modification of azimuthal angle correlation in $\Delta\phi_{\rm{j}Z}=|\phi_{\rm jet}-\phi_Z|$ and the overall suppression of average number of $Z^0$-tagged jets per boson $R_{\rm jZ}$ at $\sqrt s =5.02$ TeV as measured by the CMS experiment. We also show that higher-order corrections to $Z^0$+jet production play an indispensable role in understanding $Z^0$+jet azimuthal angle correlation at small and intermediate $\Delta\phi_{\rm jZ}$, and momentum imbalance at small $x_{\rm jZ}$. Jet quenching of the sub-leading jets is shown to lead to suppression of $Z^0$+jet correlation at small azimuthal angle difference $\Delta\phi_{\rm jZ}$ and at small $x_{\rm jZ}$.