Measurement of $\phi(1020)$ Meson Production in Fixed-Target $p\text{Ne}$ Collisions at $\sqrt{s_{NN}} = 68.5~\text{GeV}$

The first measurement of $\phi(1020)$ meson production in fixed-target $p\text{Ne}$ collisions at $\sqrt{s_{NN}} = 68.5~\text{GeV}$ is presented. The $\phi(1020)$ 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 $21.7 \pm 1.4~\text{nb}^{-1}$, collected by the LHCb detector at CERN. The $\phi(1020)$ production cross-section in the centre-of-mass rapidity range of $-1.8 < y^\ast < 0$ and transverse momentum range of $800 < p_T < 6500~\text{MeV}/c$ is found to be \[\sigma = 182.7 \pm 2.7~\text{(stat.)} \pm 14.1~\text{(syst.)}~\mu\text{b/nucleon}.\] A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the $\phi(1020)$ meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.