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We extend the k ⊥ -factorization formalism for exclusive photoproduction of vector mesons to the production of electroweak Z 0 bosons. Predictions for the γp → Z 0 p and pp → ppZ 0 reactions are given using an unintegrated gluon distribution tested against deep inelastic data. We present distributions in the Z 0 rapidity, transverse momentum of Z 0 as well as in relative azimuthal angle between outgoing protons. The contributions of different flavours are discussed. Absorption effects lower the cross section by a factor of 1.5-2, depending on the Z-boson rapidity. We also discuss the production of Z 0 bosons in central inclusive production. Here rapidity and (x IP,1 , x IP,2 ) distributions of Z 0 are calculated. The corresponding cross section is about three orders of magnitude larger than that for the purely exclusive process.

First we calculate cross section for the γp → ωp reaction from the threshold to very large energies. At low energies the pion exchange is the dominant mechanism. At large energies the experimental cross section can be well described within the k t -factorization approach by adjusting light-quark constituent mass. Next we calculate differential distributions for the pp → ppω reaction at RHIC, Tevatron and LHC energies for the first time in the literature. We consider photon-pomeron (pomeron-photon), photon-pion (pion-photon) as well as diffractive hadronic bremsstrahlung mechanisms. The latter are included in the meson/reggeon exchange picture with parameters fixed from the known phenomenology. Interesting rapidity distributions are predicted. The hadronic bremsstrahlung contributions dominate at large (forward, backward) rapidities. At small energies the photon-pomeron contribution is negligible compared to the bremsstrahlung contributions. It could be, however, easily identified at large energies at midrapidities. Absorptions effects are included and discussed. Our predictions are ready for verification at RHIC and LHC.

We calculate the production of pairs of χ cJ mesons with all possible combinations of J ¼ 0, 1, 2. The production mechanism which we consider is the crossed-channel gluon exchange in the gluon-gluon fusion reaction, the mechanism relevant for large rapidity separations between χ c mesons. The salient features of the t and u-channel gluon exchange are the broad distributions in rapidity difference Δy between χ c mesons. The building blocks are the vertices g à g à → χ cJ for off-shell gluons. We stick to the color-singlet model and calculate the gluon fusion vertices in the limit of heavy quarks with nonrelativistic motion in the bound state. These vertices are used to construct the g à g à → χ cJ 1 χ cJ 2 amplitudes. We then calculate hadronlevel cross sections using the k T -factorization approach. Several differential distributions at the pp center of mass energy ffiffi ffi s p ¼ 8 TeV are shown. We briefly discuss the contribution to J=ψJ=ψ production at large rapidity separation. For reference we show some distributions for production of χ cJ 1 χ cJ 2 pairs in double parton scattering. The discussed single parton scattering mechanisms yield similar shapes of different distributions as the double parton scattering mechanisms.

Heavy nuclei at collider energies are a source of high energy Weizsäcker-Williams photons.This photon flux may be utilized to study high energy photon-nucleus interactions. Here we concentrate on the coherent diffractive production of heavy vector mesons on nuclear targets and show how it probes the unintegrated glue of the nucleus in the saturation domain. We present predictions for rapidity distributions of exclusive coherent J/Ψ and Υ mesons which can be measured by the ALICE experiment at the LHC.