Forward rapidity J/$\psi$ production as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}=$ 5.02 and 13 TeV

Abstract

The production of J/$\psi$ is measured as a function of charged-particle multiplicity at forward rapidity in proton$-$proton (pp) collisions at center-of-mass energies $\sqrt{s}=$ 5.02 and 13 TeV. The J/$\psi$ mesons are reconstructed via their decay into dimuons in the rapidity interval (2.5 $<y<$ 4.0), whereas the charged-particle multiplicity density ($\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$) is measured at midrapidity $(|\eta |<1)$. 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 ($\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta /⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta ⟩$), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean transverse momentum ($⟨p_{\mathrm{T}}⟩$) of J/$\psi$ in pp collisions exhibits an increasing trend as a function of $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta /⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta ⟩$ showing a saturation towards high charged-particle multiplicities.

arXiv comment27 pages, 8 captioned figures, 5 tables, authors from page 22, published version, figures at http://alice-publications.web.cern.ch/node/7626

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