First measurement of charm production in fixed-target configuration at the LHC

TL;DR

This paper reports the first measurement of heavy-flavour production, specifically $J/$ and $D^0$ mesons, in fixed-target mode at the LHC, providing new insights into charm production at high energies.

Contribution

It presents the first fixed-target measurements of charm production at the LHC, expanding the experimental data in this energy regime.

Findings

Measured $J/\psi$ and $D^0$ production cross sections in $p$He collisions.

No evidence found for significant intrinsic charm in the nucleon.

Results help constrain models of heavy-flavour production at high energies.

Abstract

The first measurement of heavy-flavour production by the LHCb experiment in its fixed-target mode is presented. The production of $J/\psi$ and $D^0$ mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon centre-of-mass energies of $\sqrt{s_{NN}} = 86.6 $ and $ 110.4$ ${\rm GeV}$, respectively. The $J/\psi$ and $D^0$ (including charge conjugate) production cross sections in $p{\rm He}$ collisions in the rapidity range $[2,4.6]$ are found to be $\sigma_{J/\psi} = 652 \pm 33$ (stat) $\pm 42$ (syst) nb$/$nucleon and $\sigma_{D^0} = 80.8 \pm 2.4$ (stat) $\pm 6.3$ (syst) $\mu$b$/$nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-$x$ region.