Large Transverse Momentum Meson And Isolated Photon Tagged Jets Production In Heavy-Ion Collisions

Large transverse momentum jets are produced in the hard parton scattering processes, providing the most promising channel to test and advance perturbative quantum chromo-dynamics(QCD) in the many-body environment of ultra-relativistic nuclear collisions. It is also more sensitive to the details of the in-medium parton shower dynamics than leading hadron production. The startup of the LHC facility and jet reconstruction improvement developed by experiment collaborations has stimulated new theoretical and experimental interest of jet observables. The investigation of different final state and jet sub-structure have been carried out continuously.This thesis focus on both leading hadron productions and the photon+jet productions in heavy-ion collisions.We firstly investigate the large transverse momentum spectra of identified mesons such as ρ0and η in Au+Au at200GeV and Pb+Pb collisions at2.76TeV. They are calculated within the NLO perturbative QCD improved parton model. We employee the broken SU(3) model to determine the quark and gluon fragmentation functions(FFs) of octet vector meson in a simple way with an SU(3) breaking parameters. And we are using the higher-twist approach to modified these fragmentation functions to incorporate the jet queching effect when propagating through the hot and dense medium. The jet transport parameter that controls medium modification is proportional to the initial parton density and the coefficient is fixed by the RHIC data on suppression of large pr hadron spectra. Note that the η is4times heavier that the π0, a flat suppression has been observed at RHIC in the range pr=2-10GeV/c independent of their mass. The results are in agreement with expectations of in-medium non-Abelian energy loss of the parent parton prior to its fragmentation in the vacuum. But for the inclusive ρ0production, our NLO pQCD with the medium modified fragmentation function is observed a more suppression that the STAR Data.The nuclear modification factor are also predicted in LHC and compared to the ones in RHIC. The suppression factor increases with p? was observed, the ones in Pb+Pb collisions at LHC at moderate transverse momentum pr<20GeV/c for both π0and η production are about twice smaller than that at RHIC.Secondly, since a direct photon in the central rapidity region is always accompanied by a jet in the opposite transverse direction with roughly equal transverse energy, and the photon escapes the region of strongly interacting matter unscathed, the photon can provide constraints on the energy of the away-side parton shower. Photon+jet production has been hailed as the "golden channel" to investigate the final state jet quenching effect in high-energy nucleus-nucleus collisions, where the fast parton loses a significant of its energy due to strong interactions with the QCD medium. Note that, by jet we mean the "full jet(reconstructed jet)", the collimated showers of energetic particles in the final state. The full jet tomography can investigate jet sub-structure and jet shape at different system. Moreover, the actual measured photon is prompt photon, the experiment used isolation cut to reject the background of secondary photons coming from the decays of hadrons.This thesis calculate the production of inclusive photon and prompt photon+jet up to Next-to-leading order (NLO) in heavy ion collision, based on the framework of per-turbative QCD. We start from the productions in hadron-hadron collision, consider both "direct contribution" and fragmentation contribution" of the photon. The validation of actorization of isolation criterion modified production cross section have been discussed. The sensitivity to the isolation parameters have been studied both theoretically and nu-merically. After a baseline in nucleon-nucleon collision has been established, we present the isolated photon production and isolated prompt photon+jet production due to both the cold nuclear matter effect and the final state hot nuclear matter effect.We investigate the cold nuclear matter (CNM) effects on isolated prompt photon and isolated prompt photon associated jet productions in nuclear collisions at the NLO accu-racy by using the EPS09NLO nuclear parton distribution functions and their error sets. Nuclear modification factors of isolated prompt photon and isolated prompt photon+jet productions due to CNM effects in p+A and A+A reactions at the RHIC and the LHC are provided with varying rapidity and transverse momentum of the final state photon. It is shown that the CNM effects on isolated prompt photon and photon+jet are modest, which give a small enhancement at low px region and a more obvious suppression at large Pt at central rapidity. At forward rapidity a pronounced suppression of γ as well as γ+jet is always observed. Meanwhile, the CNM effects do not affect the momentum imbalance distribution appreciably.GLV model has been employed to investigate the parton-medium interaction. We consider final-state quark-gluon plasma effects include radiative energy loss, caused by medium-induced parton splitting, and the dissipation of the energy of the parton shower through collisional interactions in the strongly-interacting matter, meanwhile a fraction of the parton shower energy is redistributed inside the jet. We discover that the effect of final-state interaction is to broaden the momentum imbalance distribution and shift it down to smaller energy of jet. We also present the3D distribution of the nuclear modification factor with respect to both transverse momentum of jet and isolated photon, and the direct comparison between RHIC and LHC in a more exclusive channel for the first time. We find our theoretical approach that combines the O(αemα2s) perturbative cross sections with the medium-induced parton splitting and parton shower energy dissipation in the QGP describes quantitatively the increase of the transverse momentum imbalance observed by the CMS experiment in central Pb+Pb reactions at (?)=2.76TeV. We also predict the case at RHIC energy.At the end of the thesis, I also discuss the newest result on hadron-jet correlations and our approach to investigate the physics basis and give some preliminary results.