Prompt inclusive production of $J/\psi$, ${\psi }^{\prime }$ and ${\chi }_c$ mesons at $\sqrt{s}$ $=$ $68.5$ $GeV$ energy within NRQCD $k_t$-factorization approach

Abstract

We discuss prompt production of $J/\psi$ mesons in proton-proton collisions at the $\sqrt{s}$ $=$ $68.5$ $GeV$ energy within NRQCD $k_t$-factorization approach using different unintegrated gluon distributions functions (UGDFs). We include both direct color-singlet production ($gg\to J/\psi g$) as well as a feed-down from ${\chi }_c\to J/\psi \gamma$ and ${\psi }^{\prime }\to J/\psi X$ decays. The production of the decaying mesons ${\chi }_c$ or ${\psi }^{\prime }$ is also calculated within NRQCD $k_t$-factorization approach. Differential distributions in rapidity and transverse momentum of $J/\psi$ are calculated and compared with experimental data of the LHCb collaborations. The LHCb fixed target data allow to test UGDFs in a new range of $x$.

Comments: 11 pages, 6 figures