Open charm production and asymmetry in $p$Ne collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=$ 68.5 GeV

A measurement of $D^0$ meson production by the LHCb experiment in its fixed-target configuration is presented. The production of $D^0$ mesons is studied with a beam of 2.5 TeV protons colliding on a gaseous neon target at rest, corresponding to a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 68.5 GeV. The sum of the $D^0$ and ${\bar{D}}^0$ production cross-section in $p$Ne collisions in the centre-of-mass rapidity range $y^{\star }\in [-2.29,0]$ is found to be ${\sigma }_{D^0}^{y^{\star }\in [-2.29,0]}=48.2\pm 0.3\pm 4.5\mu \text{b/nucleon}$ where the first uncertainty is statistical and the second is systematic. The $D^0-{\bar{D}}^0$ production asymmetry is also evaluated and suggests a trend towards negative values at large negative $y^{\star }$. The considered models do not account precisely for all the features observed in the LHCb data, but theoretical predictions including 1$\mathrm{\%}$ intrinsic charm and 10$\mathrm{\%}$ recombination contributions better describe the data than the other models considered.