The Study On Multiplicity Dependence Of ?_c~+ Production And The Reconstruction Of Heavy-flavor Hadron ?_c~0 At ALICE

The quantum theory of 1930 explained the structure of atoms well.It was believed that the smallest particles that made up the matter are protons,neutrons,and electrons.But the anomalous magnetic moments of protons and neutrons indicate that they have a deeper internal structure.It is currently accepted that the smallest building blocks of constituent materials are quarks and leptons,and their interactions can be described by standard model.When the energy density of the system is large enough,quarks and gluons can roam in a large volume,and a new material form-quark-gluon plasma(QGP)is produced.QGP can be produced in heavy ion collisions.For that,scientists have built a series of accel-erators,LHC is the world's largest energy accelerator,and ALICE is one of the largest experiments at the LHC.The analysis in this thesis is based on experimental data from ALICE.The main purpose of the ALICE experiment is to reveal the properties of the quark-gluon plasma formed under extreme conditions.In heavy ion collisions,the enhancement of baryon-to-meason ratio,strangeness enhancement,J/? suppression and etc,which are generally considered to be the signals of QGP's formation.Recently,some new phenomena have been observed in small system pp collisions:the multiplicity dependence of enhanced strangeness,the multiplicity dependence of light-flavor hadron production,and the multi-plicity dependence of heavy-flavor hadron production.About these series of phenomena,people want to know,is it possible for small system to produce QGP?Can we interpret all phenomena observed in Pb-Pb collisions based on pp collisions?Is there a unified mech-anism to describe both small system and large system?So these new phenomena provide a new perspective to understand the phenomena observed in Pb-Pb collisions,allowing people to reexamine the behavior of Pb-Pb collisions that are considered as QGP signals.In this thesis we analyzed the multiplicity dependence of Ac production in 13 TeV pp collisions by obtaining the yield of Ac in events with high multiplicity trigger and mini-bias(MB)trigger,respectively,The results were then compared with D mesons and J/?,and we found that the multiplicity dependent behavior of Ac is consistent with that of D meson and J/?.The yield under HM trigger condition is higher than that under the MB trigger condition.This analysis provided a new reference for the study on multiplicity dependent behavior of heavy-flavor hadrons in small system pp collisions,which can further help us understand the relationship and difference between the small system and the large system.