| Quantum Chromodynamics(QCD)is a gauge theory that describes the strong interaction of quarks and gluons(partons).In electrodynamics,when a charged particle is accelerated,the particle will produce electromagnetic radiation,that is,radiating photon,which is the propagator of Quantum Electrodynamics.Analogous to a high-energy collision,when we accelerate two nuclei and make them collide,the color charge inside the nucleus will radiate the gluon which is the propagator of Quantum Chromodynamics.Under the high energy limit(or under the Bjorken x limit),the parton density inside a hadron will grow rapidly.On the other hand,the gluon recombination processes tame the growth of gluon densities.Eventually,gluons inside nuclei tend to be saturation and a condensate state will be formed with high gluon densities,which is called Color Glass Condensate(CGC).The theory describing the dynamics of gluon in saturation regime is known as CGC effective field theory(EFT).One of the main purposes of the proton(deuteron)-nucleus(p/dA)collision experiments on the Relativistic Heavy Ion Collider(RHIC)and the Large Hadron Collider(LHC)is to find experimental evidences of gluon saturation.In the future,people will further explore the direct evidences of gluon saturation in the electron-ion collider(EIC).Theoretically,CGC EFT can effectively describe the gluons saturation phenomenon at the high energy limit.Through the study of gluon saturation at the high energy limit,we can deeply understand the mechanism and properties of the interaction between quarks and gluons in the initial stage of heavy-ion collisions.In this thesis,the rapidity window dependence of the ridge correlations is firstly studied in the framework of CGC EFT.Then,a normalization of two-particle correlation is proposed in a finite phase space,we choose the per-trigger yield calculated by CGC as an example to illustrate it.Finally,the fine structure of azimuthal correlation in proton-proton collision are studied.In the CGC EFT,the two-dimensional distribution of two gluon correlations is calculated in pp collision at(?)=7 TeV.We found that when the rapidity window increases,the ridge correlations in the rapidity and azimuthal directions increase.It shows that the longitudinal and transverse characteristics of ridge correlations are dependent on the longitudinal rapidity window in CGC EFT.In the large rapidity window,the enhancement of the ridge correlations is due to the strong correlation contributed by the source gluon in the CGC framework.It lays a theoretical foundation for the experiment to observe the ridge correlations in different rapidity windows and test the CGC theory.In the finite phase space,we propose that the background of two particles correlation is the convolution of two independent single-particle production in their corresponding phase spaces.By using this background for normalization,we calculated the two-dimensional correlation of two gluons under the energy of 7 TeV in the CGC framework.The result is pretty good to describe the rapidity distribution that observed in the experiment.It is better than the parameterized normalization scheme adopted by the pioneer.Its azimuthal projection also reproduces the double-peak feature caused by collimation production.We also applied this normalization scheme to the situation at higher energy(13 TeV).We see that the ridge structure is reproduced very well under this normalization scheme.In addition,the ridge structure calculated by CGC shows a weak energy dependence which is consistent with the experimental results.Finally,the azimuthal correlation of two gluons in pp collision at(?)=7 TeV is calculated by using CGC formalism,and we found that there are two peaks at △Φ=0 and πcaused by collimation production.The azimuthal correlation also shows fine structure,i.e.,bumps or shoulders structure between the two main peaks.The position of the fine structure is related to the saturated momentum,which appears at transverse momentum around 2Qsp=1.8 GeV/c.It provides the possibility for the experiment to test the CGC theory from the azimuthal correlation. |
