The Study Of Full Jet Production In Pb+Pb Collisions At LHC

Relativistic heavy-ion collision is a significant experimental tool to study physics at high energy and high density environment and then to explore quark-gluon(QGP). In the beginning of this century, the relativistic heavy-ion collider(RHIC) was built and run in Brookheaven National Laboratory in U.S. with colliding energy up to 200Gev/n.The Large Hadron Collider(LHC) was formally put into operation at CERN in 2008. It opens a new ear in the investigation of interaction mechanism of rela-tivistic heavy ion collisions and establishes a new platform to study the properties of QCD matter. With the running of experiment, a large amount of interesting data have been accumulated.The most important discovery of heavy ion programs at RHIC and the LHC is undoubtedly that a deconfined matter behaving as a perfect liquid is created in ultra-relativistic heavy ion collisions. The formation of a deconfined QCD matter in high energy hadronic collisions was suggested long ago. An important probe of the QGP formation is jet quenching. Jet-quenching is attributed to the energy loss of ener-getic partons while propagating through the QCD medium produced in the collision which leads to the suppression of high-pt particle spectra compared to proton-proton collisions. This phenomenon was successfully observed in ultra-relativistic heavy-ion collisions at RHIC and LHC.The energy loss of parton in QGP comes from several sources. Two perturbative mechanisms were put forward to quantitatively account for the observed suppression: i) Elastic parton energy loss, in which energy is lost to the QCD medium via elastic rescatterings of the hard partons off the medium color charges [3,4]. ii) Inelastic parton energy loss, where energy is lost inelastically by medium-induced soft gluon radiation. The average elastic energy loss increases linearly as a function of the medium length L, while radiative energy loss increases quadratically, which makes the latter the dominant source of energy loss for large media.The dominant experimental measurements of jet quenching is about the produc-tion of one or two hadrons with a large transverse momentum, which are only the leading fragments of a jet. The parton energy loss mechanism will not only mani-fest itself in leading particle productions, but more interestingly in full jet observ-ables. Recently in heavy-ion community a large amount of effort has been invested in measuring reconstructed jets in high-energy nuclear collisions for the first time, and theories to address the novel features of full jet tomography in relativistic heavy-ion collisions have emerged.This thesis is based on the perturbative QCD approach, using PYTHIA+JEWEL program to calculate the jet shape, fragmentation function and nuclear modification factor in p+p collision and Pb+Pb collision. We reached the following conclusions: (1)The result of jet shape in pp collision is basicly agree with the expemental data; (2)PbPb collision fragmentation function enhancement in small PT, the energy from the intermediate PT value to small PT value of transport; (3) in 100-300Gev interval, RAA spectra is not dependent on PT obviously.