Recombination mechanism for $D^0$-meson production and $D^0-\overline{D^0}$ production asymmetry in the LHCb $p+{}^{20}Ne$ fixed-target experiment

Abstract

We discuss production of neutral $D$ mesons in proton-proton collisions at the LHC (fixed target mode) in the framework of the BJM recombination model. We present rapidity and transverse momentum distributions of $D$ mesons and compare the recombination contribution to the dominant gluon-gluon fusion mechanism. Both the direct production, as dictated by the matrix element, and fragmentation of the associated $c$ or $\bar{c}$ are included. The latter mechanism generates $D$ mesons with smaller rapidities than those produced directly. We calculate the $D^0+{\bar{D}}^0$ meson distributions relevant for fixed target $p+{}^{4}He$ collisions at $\sqrt{s}$ = 86.6 GeV as well as for $p+{}^{20}Ne$ collisions at $\sqrt{s}$ = 69 GeV. The recombination component is consistent with the LHCb data and in addition results in production asymmetry. The asymmetries in $D^0-\overline{D^0}$ production as a function of rapidity and transverse momentum are shown and the cancellation of terms for direct production and associated $c/\bar{c}$ fragmentation is discussed.

Comments: 16 pages, 8 figures. arXiv admin note: text overlap with arXiv:2105.09370