Measurement of ϕ(1020) meson production in fixed-target pNe collisions at $ \sqrt{s_{NN}} $ = 68.5 GeV

The first measurement of ϕ (1020) meson production in fixed-target p Ne collisions at $\sqrt{s_{NN}}$ = 68 . 5 GeV is presented. The ϕ (1020) mesons are reconstructed in their K + K − decay in a data sample consisting of proton collisions on neon nuclei at rest, corresponding to an integrated luminosity of 21 . 7 ± 1 . 4 nb − 1 , collected by the LHCb detector at CERN. The ϕ (1020) production cross-section in the centre-of-mass rapidity range of − 1 . 8 < y * < 0 and transverse momentum range of 800 < p T < 6500 MeV/ c is found to be σ = 182 . 7 ± 2 . 7 (stat.) ± 14 . 1 (syst) μ b/nucleon. A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the ϕ (1020) meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.