Leading twist coherent diffraction on nuclei in deep inelastic scattering at small x and nuclear shadowing

AbstractWe extend the theory of leading twist nuclear shadowing to calculate leading twist nuclear diffractive parton distribution functions (nDPDFs). We observe that the quark and gluon nPDFs have different patterns of the A-dependence. It is found that the probability of diffraction in the quark channel increases with A, reaching about 30% at x∼10−4 for A∼200, and weakly decreases with Q2. In the gluon channel, the probability of diffraction is large for all nuclei (∼40% for heavy nuclei at x∼10−4 and Q02∼4 GeV2), it weakly depends on A and it decreases rather fast with increasing Q2—the probability decreases by approximately a factor of two as Q2 changes from 4 GeV2 to 100 GeV2. We also find that nuclear shadowing breaks down Regge factorization of nDPDFs, which is satisfied experimentally in the nucleon case. All these novel effects in nDPDFs are large enough to be straightforwardly measured in ultraperipheral collisions at the LHC