Forward rapidity J/ψ production as a function of charged-particle multiplicity in pp collisions at √s = 5.02 and 13 TeV

Abstract

The production of J/ψ is measured as a function of charged-particle multi plicity at forward rapidity in proton-proton (pp) collisions at center-of-mass energies √s = 5.02 and 13 TeV. The J/ψ mesons are reconstructed via their decay into dimuons in the ra pidity interval (2.5 < y < 4.0), whereas the charged-particle multiplicity density (dNch/dη) is measured at midrapidity (|η| < 1). The production rate as a function of multiplicity is reported as the ratio of the yield in a given multiplicity interval to the multiplicity integrated one. This observable shows a linear increase with charged-particle multiplicity normalized to the corresponding average value for inelastic events (dNch/dη/hdNch/dηi), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean trans verse momentum (hpTi) of J/ψ in pp collisions exhibits an increasing trend as a function of dNch/dη/hdNch/dηi showing a saturation towards high charged-particle multiplicities.