Are there any challenges in the charmonia production and polarization at the LHC?

Abstract

We analyze the inclusive prompt production of ${\psi }^{\prime }$, ${\chi }_c$, $J/\psi$ and ${\eta }_c$ mesons at the LHC using the $k_T$-factorization approach. Our consideration is based on the off-shell production amplitudes for hard partonic subprocesses, nonrelativistic QCD formalism for the formation of bound states and transverse momentum dependent (or unintegrated) gluon densities in a proton derived from Catani-Ciafaloni-Fiorani-Marchesini equation. The nonperturbative color octet transitions are treated in terms of the multipole radiation theory. We extract the corresponding long-distance matrix elements from a combined fit to transverse momentum distributions measured at various LHC experiments. We make predictions for the polarization parameters ${\lambda }_{\theta }$, ${\lambda }_{\varphi }$, ${\lambda }_{\theta \varphi }$ and the frame-independent parameter ${\lambda }^{\ast }$ and compare them to the available ${\psi }^{\prime }$ and $J/\psi$ data. Finally, we present a universal set of parameters that provides a reasonable simultaneous description for the whole body of the LHC data (on the $p_T$ distributions, relative production rates and polarization observables) for the whole charmonium family.

Comments: 24 pages, 12 figures. arXiv admin note: text overlap with arXiv:1611.10141