Central exclusive production of $eta_c$ and $chi_{c0}$ in the light-front k$_{perp}$-factorization approach

We study the exclusive production of $J^{PC}=0^{++}, 0^{--}$ charmonium states in proton-proton collisions at the LHC energies The $pp to ppeta_c$ reaction is discussed for the first time. We observe a substantial contribution from the nonperturbative domain of gluon virtualities, especially for $eta_c$ production. To model the nonperturbative region better, we utilize models of the unintegrated gluon distribution based on parametrizations of the color dipole cross-section.

Prompt hadroproduction of C-even quarkonia in the light-front $k_T$ -factorization approach

We present a new approach for the prompt production of quarkonia which is based on the $k_T$-factorization method. The production of even C-parity quarkonia proceeds via the fusion of two (off-shell) gluons. Especially in the kinematics of the LHCb experiment these processes are thus expected to be a sensitive probe of the small-$x$ gluon distribution. We calculate the relevant off-shell matrix elements in terms of the light-front wave functions of the quarkonium states. We present our results for scalar and pseudoscalar charmonia and discuss photon transition form factors as well as cross sections for prompt hadroproduction. We compare our results for the $eta_c$ to recent LHCb data.

Central exclusive production of scalar and pseudoscalar charmonia in the light-front $k_T$-factorization approach

We study exclusive production of scalar $chi_{c0}equiv chi_c(0^{++})$ and pseudoscalar $eta_c$ charmonia states in proton-proton collisions at the LHC energies. The amplitudes for $gg to chi_{c0}$ as well as for $gg to eta_c$ mechanisms are derived in the $k_{T}$-factorization approach. The $p p to p p eta_c$ reaction is discussed for the first time. We have calculated rapidity, transverse momentum distributions as well as such correlation observables as the distribution in relative azimuthal angle and $(t_1,t_2)$ distributions. The latter two observables are very different for $chi_{c0}$ and $eta_c$ cases. In contrast to the inclusive production of these mesons considered very recently in the literature, in the exclusive case the cross section for $eta_c$ is much lower than that for $chi_{c0}$ which is due to a special interplay of the corresponding vertices and off-diagonal UGDFs used to calculate the cross sections. We present the numerical results for the key observables in the framework of potential models for the light-front quarkonia wave functions. We also discuss how different are the absorptive corrections for both considered cases.