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

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 that in hadron-nucleon scattering. For the kinematics encountered at the CERN Large Hadron Collider (LHC) and at the BNL Relativistic Heavy Ion Collider (RHIC), we compare the hard diffr-active to electromagnetic (e.m.) mechanisms of hard coherent production of two jets in proton-nucleus scattering. We study the xIP,β, and A dependence of the ratio of the dijet production cross sections due to the two effects, R, at the LHC and RHIC kinematics. 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 energies exceeding those available at the DESY Hadron Electron Ring Accelerator (HERA) by a factor of ten. In contrast, the use of lighter nuclei, such as 40Ca, allows the study of the screened nuclear diffractive parton distribution. Moreover, a comparison of the dijet diffractive production to the heavy-quark-jet diffractive production will estimate the scree-ned nuclear diffractive gluon PDF, which will be measured in nucleus-nucleus ultraperipheral collisions at the LHC