ϕ Meson production at forward rapidity in p–Pb collisions at sNN=5.02 TeV and in pp collisions at s=2.76 TeV

The first study of $\phi$-meson production in p–Pb collisions at forward and backward rapidity, at a nucleon– nucleon centre-of-mass energy $\sqrt{S_{NN}}$= 5.02 TeV, has been performed with the ALICE apparatus at the LHC. The $\phi$-mesons have been identified in the dimuon decay channel in the transverse momentum ($p_T$) range 1 < $p_T$ < 7 GeV/c, both in the p-going (2.03 < y < 3.53) and the Pb-going (−4.46 < y < −2.96) directions — where $y$ stands for the rapidity in the nucleon–nucleon centre-of-mass — the integrated luminosity amounting to 5.01 ± 0.19 nb$^{−1}$ and 5.81 ± 0.20 nb$^{−1}$ , respectively, for the two data samples. Differential cross sections as a function of transverse momentum and rapidity are presented. The forward–backward ratio for $\phi$-meson production is measured for 2.96 < |y| < 3.53, resulting in a ratio ∼ 0.5 with no significant $p_T$ dependence within the uncertainties. The $p_T$ dependence of the $\phi$ nuclear modification factor R$_{pPb}$ exhibits an enhancement up to a factor 1.6 at $\phi$= 3–4 GeV/c in the Pb-going direction. The $p_T$ dependence of the $\phi$-meson cross section in pp collisions at $\sqrt s$ = 2.76 TeV, which is used to determine a reference for the p–Pb results, is also presented here for 1 < $p_T$ < 5 GeV/c and 2.5 < y < 4, for a 78 ± 3 nb$^{−1}$ integrated luminosity sample.