Incoherent diffractive photoproduction of J/ψJ/\psi and Υ\Upsilon on heavy nuclei in the color dipole approach

We calculate cross sections and transverse momentum distributions for the incoherent diffractive production of vector mesons $J/\psi$ and $\Upsilon$ on heavy nuclei. In distinction to coherent diffraction, the nucleus is allowed to break up, but except for the vector meson no new particles are produced in the reaction. Within the color dipole approach, we derive the multiple scattering expansion of the incoherent diffractive cross section as an expansion over quasielastic scatterings of the color dipole. We also compare our results to the measurement of the ALICE collaboration for incoherent $J/\psi$ production at $\sqrt{s_{\rm NN}} = 2.76 \, \rm {TeV}$ and show predictions at $\sqrt{s_{\rm NN}} = 5.02 \, \rm{TeV}$. We also briefly discuss a possible contribution to $J/\psi$ production in peripheral collisions in the $70 \div 90 \%$ centrality class.Comment: 18 pages, 8 fig

Exclusive photoproduction of charmonia in γp→Vp\gamma p \to V p and pp→pVpp p \to p V p reactions within ktk_t-factorization approach

The amplitude for $\gamma p \to J/\psi p$ ($\gamma p \to \psi' p$) is calculated in a pQCD $k_{T}$-factorization approach. The total cross section for this process is calculated for different unintegrated gluon distributions and compared with the HERA data and the data extracted recently by the LHCb collaboration. The amplitude for $\gamma p \to J/\psi p$ ($\gamma p \to \psi' p$) is used to predict the cross section for exclusive photoproduction of $J/\psi$ ($\psi'$) meson in proton-proton collisions. Compared to earlier calculations we include both Dirac and Pauli electromagnetic form factors. The effect of Pauli form factor is quantified. Absorption effects are taken into account and their role is discussed in detail. Different differential distributions e.g. in $J/\psi$ ($\psi'$) rapidity and transverse momentum are presented and compared with existing experimental data. The UGDF with nonlinear effects built in better describe recent experimental data of the LHCb collaboration but no definite conclusion on onset of saturation can be drawn. We present our results also for the Tevatron. A good agreement with the CDF experimental data points at the midrapidity for both $J/\psi$ and $\psi'$ is achieved.Comment: 15 pages, 19 figure

Photoproduction of J/ψJ/\psi and Υ\Upsilon states in exclusive and proton-dissociative diffractive events

The amplitude for $\gamma p \to V p$, where $V$ is a $J/\psi$ or $\Upsilon$ ground state or excited vector meson, is calculated in a pQCD $k_{T}$-factorization approach. We use this amplitude to predict the cross section for exclusive photoproduction of $J/\psi, \psi', \Upsilon$ mesons in proton-proton collisions. Calculations are performed for a variety of unintegrated gluon distributions, and we compare our results to LHCb data. Here we especially focus on the possibilty of constraining saturation effects. Compared to earlier calculations we include both Dirac and Pauli electromagnetic form factors. We discuss the role of the $Q\bar Q$ light-cone wave functions for differential distributions for ratios such as $\sigma(\psi')/\sigma(J/\psi)$. Absorption effects are always taken into account. We also discuss the related diffractive production in proton dissociative events. Here we concentrate on electromagnetic dissociation , which is calculable without additional free parameters. Besides being of interest in their own right, dissociative events constitute an important experimental background to exclusive production.Comment: 6 pages, 5 figures, Talk given by WS at the XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects, 11-15 April, 2016, DESY Hamburg, German

Production of W+W−W^+ W^- pairs via γ∗γ∗→W+W−\gamma^*\gamma^* \to W^+ W^- subprocess with photon transverse momenta

We discuss production of $W^+ W^-$ pairs in proton-proton collisions induced by two-photon fusion including, for a first time, transverse momenta of incoming photons. The unintegrated inelastic fluxes (related to proton dissociation) of photons are calculated based on modern parametrizations of deep inelastic structure functions in a broad range of their arguments ($x$ and $Q^2$). In our approach we can get separate contributions of different $W$ helicities states. Several one- and two-dimensional differential distributions are shown and discussed. The present results are compared to the results of previous calculations within collinear factorization approach. Similar results are found except of some observables such as e.g. transverse momentum of the pair of $W^+$ and $W^-$. We find large contributions to the cross section from the region of large photon virtualities. We show decomposition of the total cross section as well as invariant mass distribution into polarisation states of both W bosons. The role of the longitudinal $F_L$ structure function is quantified. Its inclusion leads to a 4-5 % decrease of the cross section, almost independent of $M_{WW}$.Comment: 20 pages, 17 figures, 2 table