Measurement of $J/\psi$ and $D^0$ production in $p$Ar collisions at $\sqrt{s_{NN}}=110$ GeV

The first analysis of heavy flavour production measured by the LHCb experiment in fixed-target mode is presented. The $J/\psi$ and $D^0$ production processes are studied in 6.5 TeV proton-beam-induced reactions on an argon gaseous target. About 500 $J/\psi \to \mu^+ \mu^-$ and 6500 $D^0 \to K^- \pi^+$ decays are reconstructed. Their yields are studied as a function of transverse momentum, rapidity, Bjorken-$x$ and Feynman-$x$. No strong dependence of the $J/\psi / D^0$ cross-section ratio on rapidity is observed.