Color Glass Condensate Effective Theory And Its Applications In High Energy Scattering

In this thesis,we focus on small x physics(or saturation physics)and color glass condensate effective theoryIn high energy scattering,Regge-Gribov limit refers to the kinematic region where for giving value of Q2,x approaches to 0 and s approaches to oo.It has been found that gluon density grow rapidly rapidly as x decreases in experiment which corresponds to the linear terms in the evolution equation.But,the unitary bound tells us that it can not grow without limit.As the gluon density growing,nonlinear effects become important and the growth rate is slowed.This is called saturation,and color glass condensate effective theory is the theory describes it.The Color Glass Condensate(CGC)is the description of the properties of sat-urated gluons in the infinite momentum frame(IMF)in the Regge-Gribov limit.An extra semi-hard scale emerges in this state of matter which justify the possibility of pertubative calculation.Color glass condensate effective theory includes two parts.One is the classical description of the high density gluons and the other is the non-linear evolution equation of color source which resums all the important quantum corrections.This thesis covers three topics:Sudakov suppression of the Balitsky-Kovchegov kernel BK equa-tion is the mean-field truncation of the non-linear evolution equation in color glass condensate effective theory and it plays a central role in studying satura-tion physics.However,when trying to solve the NLO BK equation numerically,it was found to be unstable.This is essentially due to the NLO correction enhanced by double logarithms,which becomes very large when the parent dipole is much smaller than the daughter dipole.To sum high-energy leading logarithms in a consistent way,one has to impose the strong ordering in both projectile rapidity and dense target rapidity simultaneously,which results in a kinematically improved Balitsky-Kovchegov(BK)equation.We find that beyond this strong ordering region,the important sub-leading double logarithms arise at high order due to the incomplete cancellation between real corrections and virtual corrections in a t-channel calculation.Based on this observation,we further argue that these double logarithms are the Sudakov type ones,and thus can be resummed into an exponential leading to a Sudakov suppressed BK equation.Sea quark Sivers distribution Polarization dependent phenomenology at small xhas attracted a lot of attention in recent years,as it plays an important role in studying gluon tomography of nucleon/nuclei.We compute sea quark Sivers distribution within color glass condensate(CGC)framework.It has been found that up to the leading logarithm accuracy,the collinear twist-3 approach and the CGC calculation yield the same result for sea quark Sivers distribution in the dilute limit.We further verify that transverse momentum dependent factorization is consistent with CGC treatment at small xfor the case of transverse single spin asymmetry in open charm quark production in semi-inclusive deeply inelastic scattering process in an overlap kinematical region.Studying Coulomb correction at EIC and EicC Color glass condensate effective theory is the description of QCD in strong gluon field,and similarly,QED process in strong electromagnetic field also attracts a lot of attentions many years ago.The study of QED processes in astrong Coulomb field has a long history pioneered by the Bethe and Maximon's seminal work in 1950s.It later received renewed interest in the heavy ion physics community around the time when physics operation began at the Relativistic Heavy Ion Collider(RHIC).A lot of efforts have been made to compute pure electromagnetic lepton pair production in Ultra-Peripheral heavy ion Collisions(UPC)to all orders in Zalpha where Z is the nuclear charge number.We study the gauge link contribution to the dipole type transverse momentum dependent distributions of coherent photons,which is conventionally referred to as the Coulomb correction.We further propose to search for the evidence of the Coulomb correction in the Bethe-Heitler process in eA collisions at EIC and EicC.