V⁰-Charged Hadron Correlation In Pb-Pb Collisions At ?^S?NN??^1/2= 5.02 TeV With ALICE

Up to now,scientists believe that subatomic particles consist of quarks and leptons,and atoms are composed of protons and neutrons.In general,we can not observe isolated quarks and gluons as quarks and gluons are confined to hadrons.But there is theory that when the temperature and energy density exceed the critical value of the theoretical prediction,a new state of matter that consists of quarks and gluons will be formed.And the new matter is called quark-gluon plasma(Quark-Gluon Plasma,QGP).In the present condition,we can only use the relativistic heavy ion collision experiment to produce QGP,and to study the properties of QGP by exploring signal probes.One of the probes that can prove the existence of QGP is jet quenching.The modification of the per-trigger yield of associated particles,IAA,has been extracted from dihadron correlations in Pb-Pb collisions at(?)= 2.76 TeV.In central colliisons,on the away side,suppression is observed as expected from strong in-medium energy loss.Near side enhancement suggests that the near-side parton is also subject to medium effects.In peripheral collisions,both the near and away side IAA approach unity,as expected in the absence of medium effects.The per-trigger yield modification factor,IAA,has been measured from two-particle correlations with neutral pions as trigger particles in 0-10%most central Pb-Pb collisions.On the away side,the per-trigger yields in Pb-Pb are strongly suppressed to the level of IAA ? 0.6 for pTassoc>3 GeV/c.On the near side,an enhancement of IAA between 1.2 to 1.8 at lowest pTassoc is observed.Only AMPT is able to capture the enhancement at low pTassoc and describe the away-side suppression at high pTassoc.The coincidence of the away-side suppression at high pTassoc and the large enhancement at low pTassoc on the near and away sides is suggestive of a common underlying mechanisms,likely related to the energy lost by high momentum partons.At present,with the increase of multiplicity,the ratio of baryon to meson shows similar behaviors,which are significant enhancement at intermediate transverse mo-mentum interval(2<pT<6 GeV/c)with increasing multiplicity and corresponding significant depletion in the low transverse momentum interval(pT<2 GeV/c),as observed in p-p,p-Pb and Pb-Pb collisions.The more the multiplicity,the more significant the effect of depletion.In addition,the more the multiplicity,the more significant the effect of enhancement.There are two explanations for the depletion effect in the low transverse momentum interval and the enhancement effect in inter-mediate transverse momentum interval.The first explanation is that they are due to the radial flow of the soft process.The second one is that they are due to the effect of hadronization mechanism.The trigger is chosen in intermediate pT,then it will include hard triggers as well as soft triggers.The soft triggers will not contribute to jet-like yield,but since we extract the per-trigger yield by normalizing with the number of triggers,these will create a dilution in the yield.In heavy-ion collision-s,there is jet quenching in medium.The intermediate pr particles,produced from jet-medium interaction,can affect jet-yield also.Therefore,the dilution can not be di-rectly related to coalescence.Now,this trigger dilution is observed in p-Pb,Au-Au,Cu-Cu collisions.In view of the current research status at home and abroad,this present work is based on the analysis of Pb-Pb collisions at(?)= 5.02 TeV recorded with ALICE at the LHC.In this analysis,we choose neutral strangeness(1<pT<15 GeV/c)as trigger particles,and charged hadrons(1<pT<8 GeV/c)as the associated particles.By using the method of two particle correlations,we can extract the associated per-trigger yield in centrality 0-10%.The purpose of this study is to explore the effect of different charged hadrons as trigger particle on the associated per-trigger yield,trigger dilution,the production mechanism of neutral strangeness particles,and the reasons for the depletion effect in the low transverse momentum interval and the enhancement in intermediate transverse momentum interval.In the first chapter of this thesis,quark-gluon plasma,its signal probes,and the research status of the enhancement in the intermediate transverse momentum,and the motivation of this work,are introduced.Chapter 2 introduces the ALICE detector,focusing on some sub-detectors used in this analysis.Chapter 3 elaborates the selections that prepare for building V0-charged hadron correlations,how to build correlation,corrections for correlation and so on.Chapter 4 shows extraction of associated per-trigger yields.Chapter 5 shows the summary and outlook of this thesis.