Exclusive Charmonium Photo-Production at HERA and LHC with Color Glass Condensate

We calculate the exclusive charmonium photo-production in the framework of color glass condensate.To obtain a good description of the vector meson production experimental data at HERA,we introduce a vector meson mass dependent skewness factor into the skewness effect.Then we extend the skewness improved model to the LHC energies.The numerical results of our model are in good agreement with theΨ/Ψ and Ψ（2S）data in ultraperipheral proton-proton collisions at LHC,which show the significance of the vector meson mass-dependent skewness factor.A prediction of the exclusive charmonium photo-production in ultra-peripheral nucleus-nucleus collisions is performed since it can provide a good way to test the effectiveness of the color glass condensate.

Exclusive photoproduction of vector meson at next-to-leading order from color glass condensate

The exclusive photoproduction of vector mesons(J/ψ/andφ)is investigated by considering the next-toleading order corrections in the framework of the color glass condensate.We compare the next-to-leading order modified dipole amplitude with the HERA data,finding a good agreement.Our studies show that theχ~2/d.o.f from the leading order,running coupling,and collinearly improved next-to-leading order dipole amplitudes are 2.159,1.097,and 0.932 for the elastic cross-section,and 2.056,1.449,and 1.357 for the differential cross-section,respectively.The results indicate that the higher-order corrections contribute significantly to the vector meson productions,and the description of the experimental data is dramatically improved once the higher order corrections are included.We extend the next-to-leading order exclusive vector meson production model to LHC energies using the same parameters obtained from HERA.We find that our model provides a rather good description of the J/ψandΦdata in proton-proton collisions at 7 TeV and 13 TeV in LHCb experiments.

Probing valence quark width of the proton in deeply virtual Compton scattering at high energies

We use the refined hot spot model to study the valence quark shape of the proton with the deeply virtual Compton scattering at high energies in the color glass condensate framework.To investigate the individual valence quark shape,a novel treatment of the valence quark width is employed.We calculate the cross-sections for coherent and incoherent deeply virtual Compton scattering using,for the first time,different widths(Bu and Bd)for the profile density distributions of the up and down quarks instead of using the same width as in the literature.We find that the cross-sections calculated with Bu≥Bd at each collision energy are consistent with each other,which is in agreement with theoretical expectations,whereas those computed with Bu<Bd show some discrepancies.This outcome implies that the up quark might emit more gluons than the down quark,leading to Bu≥Bd at high energy.The impact of energy on the outcome is estimated.Our results show that as the collision energy increases,the aforementioned discrepancies are not only significantly broadened,but also shift to a relatively smaller momentum transfer range at the future Electron-Ion Collider(EIC)and Large Hadron Electron Collider(LHeC)energies,which indicates that the EIC and LHeC can provide an unprecedented chance to access the shape of the valence quark of the proton.

Analytic expression for the proton structure function in deep inelastic scattering

The analytic expression of proton in deep inelastic scattering is studied by using the color glass condensate model and the dipole picture. We get a better description of the HERA DIS data than the GBW model which was inspired by the Glauber model. We find that our model satisfies the unitarity limit and Froissart Bound which refers to an energy dependence of the total cross-section rising no more rapidly than ln^2 s.

Hadron production with collinearly-improved unintegrated gluon distributions in high energy proton-proton collisions

The collinearly-improved Balitsky-Kovchegov(ciBK)equation evolved unintegrated gluon distribution(UGD)is used for the first time to study hadron production in high energy proton-proton collisions in order to improve the predictive power of the Color Glass Condensate effective theory.We show that the ciBK equation evolved UGD provides a relatively better description of LHC data on the transverse momentum and integrated multiplicity distributions of charged hadron and neutral pion production for several collision energies compared with the running coupling Balitsky-Kovchegov(rcBK)equation evolved UGD.This is because the ciBK evolved UGD has a sharper transverse momentum distribution than the rcBK UGD.The impact of running coupling prescriptions on hadron production is studied,and it is found that the parent dipole and smallest dipole running coupling prescriptions provide similar depictions of the data.Moreover,the scale dependence of the fragmentation function is investigated by taking three typical values of scale.We find that the differences resulting from the scale dependence of the fragmentation function can be fully absorbed into the normalization factor,which lumps higher order corrections.

Statistical physics in QCD evolution towards high energies

The concepts and methods used for the study of disordered systems have proven useful in the analysis of the evolution equations of quantum chromodynamics in the high-energy regime: Indeed, parton branching in the semi-classical approximation relevant at high energies and at a fixed impact parameter is a peculiar branching-diffusion process, and parton branching supplemented by saturation effects(such as gluon recombination) is a reaction-diffusion process. In this review article, we first introduce the basic concepts in the context of simple toy models, we study the properties of the latter, and show how the results obtained for the simple models may be taken over to quantum chromodynamics.

Gluon saturation and pseudo-rapidity distributions of charged hadrons at RHIC energy regions

We modified the gluon saturation model by rescaling the momentum fraction according to satu- ration momentum and introduced Cooper-Frye hydrodynamic evolution to systematically study the pseudo- rapidity distributions of final charged hadrons at different energies and different centralities for Au-Au collisions in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider （RHIC）. The features of both gluon saturation and hydrodynamic evolution at different energies and different centralities for Au-Au collisions are investigated in this paper.