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.

Exclusive and dissociative J/ψproduction with collinear-improved Balitsky-Kovchegov equation

We extend the hotspot model to include the virtuality dependence and use it to study the exclusive and dissociative J/Ψ production combined with the dipole amplitude in the target rapidity representation.We determined that virtuality takes effect on a number of hotspots,thus providing a better description of the J/Ψ production data at HERA.The collinear improved Balitsky-Kovchegove equation in the target rapidity representation is numerically solved and used to fit the J/Ψ experimental data with a series of hotspot sizes.We infer that virtuality significantly influences the number and size of hotspots.The expression χ^(2)/d.o.f=1.0183 resulting from the fit with the collinear improved dipole amplitude in the target rapidity representation is more reasonable than the correspondingχ^(2)/d.o.f=1.3995 originating from the leading order fit,which indicates that the collinear improved evolution equation in the target rapidity representation can provide a relatively good depiction of the exclusive and dissociative HERA data.