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 quarkgluon 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 xjZ = p jet T /p Z T , the modification of azimuthal angle correlation in ∆φjZ = |φjet − φZ | and the overall suppression of average number of Z 0 -tagged jets per boson RjZ at √ 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 ∆φjZ, and momentum imbalance at small xjZ. Jet quenching of the sub-leading jets is shown to lead to suppression of Z 0 +jet correlation at small azimuthal angle difference ∆φjZ and at small xjZ.

In this study, the production of inclusive b-jet and dijets in Pb + Pb collisions has been investigated by considering the in-medium evolution of heavy and light quarks simultaneously. The initial hard processes of inclusive b-jet and dijets production are described using a next-to-leading order (NLO) plus parton shower Monte Carlo (MC) event generator, SHERPA, which can be well matched with the experimental data in p + p collisions. The framework uses the Langevin transport model to describe the evolution of the bottom quark. Furthermore, the collisional energy loss and higher-twist description are considered to determine the radiative energy loss from both the bottom and light quarks. We compare the theoretical simulation of the inclusive jet and b-jet in the Pb + Pb collisions at TeV with the experimental data and present the theoretical simulation of the momentum balance of the dijet in the Pb + Pb collisions at TeV along with recent CMS data for the first time. A similar trend to that seen in inclusive dijets is observed in dijets; the distribution of the production shifts to smaller owing to the jet quenching effect. Finally, we report the prediction of the normalized azimuthal angle distribution of the dijet in the Pb + Pb collisions at TeV. The medium-induced energy loss effect of the dijets will generally suppress its production; however, the same side ( region) suffers more energy loss than the far side ( region), thus leading to suppression on the same side and enhancement on the far side in the normalized azimuthal angle distribution in A + A collisions.

We present the first theoretical study of medium modifications of the global geometrical pattern, i.e., transverse sphericity ($$S_{\perp }$$ S ⊥ ) distribution of jet events with parton energy loss in relativistic heavy-ion collisions. In our investigation, POWHEG + PYTHIA is employed to make an accurate description of transverse sphericity in the p + p baseline, which combines the next-to-leading order (NLO) pQCD calculations with the matched parton shower (PS). The Linear Boltzmann Transport (LBT) model of the parton energy loss is implemented to simulate the in-medium evolution of jets. We calculate the event normalized transverse sphericity distribution in central Pb + Pb collisions at the LHC, and give its medium modifications. An enhancement of transverse sphericity distribution at small $$S_{\perp }$$ S ⊥ region but a suppression at large $$S_{\perp }$$ S ⊥ region are observed in A + A collisions as compared to their p + p references, which indicates that in overall the geometry of jet events in Pb + Pb becomes more pencil-like. We demonstrate that for events with 2 jets in the final-state of heavy-ion collisions, the jet quenching makes the geometry more sphere-like with medium-induced gluon radiation. However, for events with $$\ge 3$$ ≥ 3 jets, parton energy loss in the QCD medium leads to the events more pencil-like due to jet number reduction, where less energetic jets may lose their energies and then fall off the jet selection kinematic cut. These two effects offset each other and in the end result in more jetty events in heavy-ion collisions relative to that in p + p.

We report a systematic study of Z+jet correlation in Pb+Pb collisions at the LHC by combining the next-leadingorder matrix elements calculations with matched parton shower in Sherpa for the initial Z+jet production, and Linear Boltzmann transport Model for jet propagation in the expanding quark-gluon-plasma. Our numerical results can well explain CMS measurements on Z+jet correlation in Pb+Pb collisions: the shift of p T imbalance x jZ = p jet T /p Z T and their mean values, the suppression of the average number of jet partners per Z boson R jZ , as well as the modification of azimuthal angle correlations ∆φ jZ . We also demonstrate that high-order corrections play a significant role in the understanding of Z+jet correlations at high energies.

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