Charged Hadron-V~0 Correlation In P-Pb Collisions At (?)= 5.02 TeV With ALICE

It is generally agreed that the tectonic units of atomic nuclear are subatomic particles,such as protons and neutrons,and subatomic particles are composed of quarks and other microscopic particles in modern physics research.With the impact of strong force which is transmitted through gluon,the quarks are combined into protons and neutrons.In general,they cannot exist independently but be bounded in nucleus.However,lattice QCD predicts the quark deconfinement in the condition of large enough energy and high enough temperature,forming a new state of matter-quark-gluon plasma(QGP)which is different from protons and neutrons.The QGP state might exist right after Big Bang(extremely high temperature)and the interior of collapsing neutron star(high baryon density).In order to find QGP and study its properties,physicists are expecting to produce it by high energy heavy-ion collision experiments,therefore a series of accelerators have been built,such as SPS,RHIC,LHC and etc.A sequence of remarkable progress has been achieved on the study of QGP.The world's largest and most powerful particle accelerator,Large Hadron Collider(LHC)which is also the latest addition to the accelerator complexus of the European Organization for Nuclear Research(CERN).There are four large experiments at LHC.Among them,a large ion collider experiment(ALICE),which aims at simulating the formation process of original universe after Big Bang and analysing the properties of QGP,not only extends the territory of physics close to the initial state of universe,but also has great significance to the investigation of the evolution of universe and the nature of matter and to the verification of the existing standard model in particle physics.However,we cannot directly observe the process of collision and its evolution,but only probe the QGP formation through measuring the final products.There are several probes which are used to the formation of QGP of the collisions:the phenomenon of collective flow,jet quenching,the generation of direct photons,the enhancement of strangeness particle yield and etc.Compared to the p-p collisions,an enhancement of baryon to meson ratio(e.g.?/KS0)in the intermediate transverse momentum range of 2<pT<6 GeV/c is ob-served in heavy-ion collisions.And the magnitude of enhancements diminishes from the central collision to the peripheral collisions.Some research results indicate that the enhancement is the joint effect of hadronization mechanism and QGP expan-sion dynamics(radial flow).The enhancement effect also exists in the intermediate transverse momentum range of 2<pT<6 GeV/c in p-Pb collisions.What's more,the peak ratio is obtained in central collision,which is the same as Pb-Pb collisions.This thesis aims at investigating whether a dense medium is also produced in p-Pb collisions or the enhancement in Pb-Pb collisions results partially from cold nuclear matter effects.The present dissertation work is based on the analysis of p-Pb data at(?)=5.02 TeV recorded with ALICE at the LHC in 2013.The two-hadron correlation distributions are constructed with charged primary hadrons(5<pT<15 GeV/c)as trigger particles and A and KS0strange hadrons(1<pT<7 GeV/c)as associated particles.Results on A/KS0,related to bulk region and jet region,will be presented for different intervals of centrality of the collisions(0-10%,10-40%,40-100%centrality classes),with the aim of figuring out whether the baryon-to meson enhancement is due to soft process or hard processes.In the first chapter of the thesis,the theoretical background related to heavy-ion collisions,quark-gluon plasma,as well as the experimentally observed baryon-to-meson enhancement will be introduced.In chapter 2,the ALICE detector and the main subsystems used in the analysis will be briefly described.Chapter 3 describes the selections applied in order to perform the two-hadron angular correlations,as well as the various steps and corrections used to construct these correlations.Chapter 4 presents the main results of the data analysis(the per trigger yield of A and KS0 in the bulk and the near-side peak regions).The following chapter is a summary and outlook.