The Study Of The Real Photon-like Structure On The Electron-heavy Ion Collider

A photon is a fundamental ingredient of our present understanding of the interactions of quarks and leptons.Being the gauge boson of the theory of quantum electrodynamics(QED),the photon mediates the electromagnetic force between charged objects as a massless particle.While in the framework of quantum chromodynamics(QCD),the quanta themselves can develop a structure.Due to the Heisenberg uncertainty principle written as ?E?t>1,the high energy photon can have an energy fluctuation by an amount of ?E for a short period of time At.During such a fluctuation,the photon is allowed to split into a charged fermion-antifermion pair,f f,carrying the same quantum numbers as the photon.Based on this,the photon naturally becomes an important object for research on particle physics.According to QCD,the photon is a superposition of a bare photon state which inter-acts only with electric charges,and a hadronic photon state which is called the resolved photon.If probed experimentally at very short distances,the intrinsic structure of the resolved photon is recognized as a flux of quark and gluon components,quasi-free ac-cording to asymptotic freedom in QCD.The interaction between the resolved photon and other particles is therefore interpreted as an incoherent superposition of scatterings on the fundamental constituent quarks and gluons,leading us to a universal parton dis-tribution function(PDF)describing the quark and gluon densities of the photon.The PDFs of the photon are functions of the momentum fraction,x,carried by the partons within the photon and the scale,Q2,at which the densities are probed.A future electron ion collider(EIC),named eRHIC at Brookhaven National Labora-tory,will be able to provide collisions of polarized electrons with protons and heavy ions over a wide range of center-of-mass energies(20 GeV to 140 GeV)at an instantaneous luminosity of 1033-1034 cm-2s-1.Measuring di-jets in quasi-real photoproduction events,one can effectively access the underlying parton dynamics of the photons.In this thesis,we present a di-jet method applied on the EIC to investigate the structure of photon experimentally.We discuss firstly how jets are reconstructed at the EIC.The basic jet kinematics,background due to underlying events and quark/gluon jet discrimination are studied as well.Secondly we discuss the possibility for the photon to interact either directly or in a resolved manner.We provide an expermental method to tag resolved photon processes and measure the di-jet cross section as a function of jet transverse mo-mentum in the range of 0.01<x?rec<1 at the EIC.It will be shown that both unpolarized and polarized parton distributions in the photon can be extracted,and that the flavor of the parton can be tagged at the EIC.