Leading-twist nuclear shadowing and suppression of hard coherent diffraction in proton-nucleus scattering

Abstract

We use the Glauber-Gribov multiple scattering formalism and the theory of leading twist nuclear shadowing to develop a method for the calculation of leading twist hard coherent diffraction in hadron-nucleus processes. We demonstrate that soft multiple rescatterings lead to the factorization breaking of hard diffraction in proton-nucleus scattering, which is larger than in hadron-nucleon scattering. At the LHC and RHIC kinematics, we compare the hard diffractive to e.m. mechanisms of hard coherent production of two jets in proton-nucleus scattering. We study the xIP, � and Adependence of the ratio of the dijet production cross sections due to the two effects, R. We demonstrate that in proton-heavy nucleus hard coherent diffraction at the LHC, R is small, which offers a clean method to study hard photon-proton scattering at the energies exceeding the HERA energies by the factor of ten. On the other hand, the use of lighter nuclei, such as 40 Ca, will allow to study the screened nuclear diffractive parton distribution. Moreover, a comparison of the dijet diffractive production to the heavy-quark-jet diffractive production will estimate the screened nuclear diffractive gluon PDF, which will be measured in nucleus-nucleus ultraperipheral collisions at the LHC.