π~0 Meson Production In P-P Collision At 5.02 TeV With ALICE At The LHC

Lattice quantum chromodynamics (LQCD) predicted extremely high temperature and density conditions will lead quark hadron to a new state of matter- the quark- gluon plasma (QGP). This is a major issue in the field of today’s cutting-edge physics.In accordance with the Standard Model, the basic structure of matter is composed of quarks and leptons which interacting with each other. Standard Model proposed minimum component composition of material are quarks (u, d; s, c; b, t), leptons (e, ve; μ, vμ; τ, vτ) and interaction transfer media, such as W± particle, Z0 particles, gluons and photons..Depending on the media, the fundamental forces can be into the electromagnetic interaction, the weak interaction and the strong interaction. They built up a subatomic level togetherSince the total color charge must be zero, so quarks with color charge bound in hadrons, and cannot be separated individually, so people call it "quark confinement." However, under extreme conditions of high temperature or high density, hadron with quark confinement phase may deconfinement to quark-gluon plasma phase. Lattice QCD predicted the temperature which quark deconfinement from hadron phase to the free state Therefore, people build a lot of high energy experimental apparatus dedicated to detecting the signal of quark matter and its properties..The Large Hadron Collider which in the European Organization for Nuclear Research is the highest energy particles accelerator in the world today. A Large Ion Collider Experiment is an experiments which doing the lead-Lead (Pb-Pb) collision in the TeV energy level in the LHC.QGP substances very short time, so people can only measure the end state of collision to study QGP’(?)srRSHtUrJ/QGP^ctfygHJfOHjJQWSH1? HDyH g/ψ yields down, strange particle reinforced, generation of heat photons and leptons, jet quenching and high transverse momentum partic (?)(?)(?)JtfcQ DQPJrFSc flow in final state is not zero, etc.Direct photons produced in the early stage of collision, and photons only have interaction with other things through electromagnetic force. So direct photons have a long mean free path and through the nucleus-nucleus collisions produce hot dense matter almost unaffected. This means direct photon carry the information of initial stage of collision. Experimentally, the direct photons are rarely, mostly photons are decay photons from π0 meson. By measuring the decay photons, one can calculated π0 meson spectrum to support the study of nuclear correction factors and QGP. The proton-proton collisions in the TeV level of energy will generate a lot of π0 mesons. Measure π0 particle spectrum can help us test QCD theory predicts and support the study of π0 meson spectrum down in the nuclear-nuclear collisionsElectromagnetic calorimeter in ALICE can detect photons from 0.5 GeV Ic to 100 GeV /c. This paper combined the data from electromagnetic calorimeter and the ALICE platform to study π0 meson spectrum. The first chapter describes the Standard Model and quantum chromodynamics, and high-energy heavy ion collisions. The second chapter GeverIEevthe A/’CE exSerlmeCt’vGetectorVand functions, ALICE Offline platform and Aliroot. The third chapter describes the π0 meson invariant mass reconstruction, data quality assessment, background removed, π0 meson raw spectrum, π0 reconstruction efficiency and the π0 meson raw spectrum after efficiency correction. The fourth chapter of the thesis is summary and outlook.