Study Of Final State Effects On Jet Hadronization And Neutral Pion Measurement With ALICE Detector

Lattice Quantum Chromodaynamics(LQCD)predicts that at high temperature and high density a deconfined phase from hadronic matter to quark-gluon plasma(QGP)will occur.In the well-known theory of Big Bang,there can create a high temperature and high density condition in the Big Bang initial stage,so we believe that in this stage a quark-gluon plasma can be produced.In order to explore the properties of this new kind of phase,physicists have designed heavy ion collisions experiment and various models to simulate the heavy ion collisions.RHIC and LHC are the representative in experiments.And there are many simulation models,such as PYTHIA,HIJING,and PYQUEN.In the RHIC experiment,we find that,comparing with the d-Au collision,the Au-Au collision's final hadrons,there are a obviously suppression no matter in the high pt or in the low pt.From this we can know that in high-energy nuclear collisions when the parton transport through the collisions to create new matter,the parton lost a part of energy.We call this phenomenon jet quenching.However,compared the p-Pb collisions with the pp collisions,there also are similar class collective effect.Because of this,we double that if this phenomenon can happen in the cold nucleus effects.We mainly introduce the high-energy heavy ion collisions.And we use pp collisions as reference to explore some specific properties of the new matter—QGP.Besides of the phenomenon of jet quenching,many other experiment groups also find other evidence to prove the existence of QGP,such as the increase of strange particles,the suppression of J/?yield,collective flow effects and so on.However in the high-energy pp collisions we also observed the final particles,collective effect--the increase of baryon meson ratio.Because of this phenomenon,we begin to double if there also has QGP in the high-energy pp collisions and p-Pb collisions.So that we consider that in the no QGP environment if the initial parton fluctuation and the color recombination effect in hadronic process have class collective effect on the final jet hadronization.This will help us to understand the class collective effect of final jet hadronization on small systems.In addition,we try to add the gluon radiative energy loss to the final jet hadronic process,so that to observe the change of the final jet.We mainly introduce two simulation models.One is Pythia and another is PyQuen.Through this two models,we study the influence of different color reconnection models and energy loss with different angles on the final jet hadronic process.We learn from new QCD color reconnection model and high multiplicity interaction(MPI)color recombination model to analyze different simulations.Then through adding different angles gloun radiative energy loss to final jet,then we get different models'results.Last we compare and analyze the result.In order to get a better understanding of jet production,we go to experiments to research the final jet production.And studying direct photon-jet correlations is a good way to get the goal.In this study,we need to clarify the direct photon.In experiments,di-photon decaying from neutral pion is the biggest background of the direct photon.So that,we need to find the corresponding neutral pion.In ALICE,we use the advantages of detecting particle tracks in central area and Electromagnetic calorimeter of neutral pion to verify the neutral pion,thereby we screen out the partially decay photon from direct photon.So that we can get a better study of direct photon-jet.when getting many informations of jet in the simulation models.we can analyze and study the specific source of collective effect more intuitively in the pp collisions and p-Pb collisions.And simulations have positively effects on the study of cold nuclear effect.At last,it also can help us to answer the question that dose QGP really exists in small systems.In the future,experiments go to higher energy,data become more perfect and simulation system become more in-depth,then we can achieve the goal of exploring the microcosm through the deep study of the jet.