• Energy Research

The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of $J/��$ vector mesons off proton targets in ultra-peripheral p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV. The e$^+$e$^-$ and $��^+��^-$ decay channels are used to measure the cross section as a function of the rapidity of the $J/��$ in the range $-2.5 < y < 2.7$, corresponding to an energy in the $��$p centre-of-mass in the interval $40 < W_{��\mathrm{p}}<550$ GeV. The measurements, which are consistent with a power law dependence of the exclusive $J/��$ photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements. 25 pages, 3 captioned figures, 3 tables, authors from page 19, published version, figures at http://alice-publications.web.cern.ch/node/4554

Abstract Inclusive J/ψ production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of $$ \sqrt{s} $$ s = 5.02 TeV by ALICE at the CERN LHC. The measurement is performed at mid-rapidity (|y| < 0.9) in the dielectron decay channel down to zero transverse momentum p T, using a data sample corresponding to an integrated luminosity of L int = 19.4 ± 0.4 nb −1. The measured p T-integrated inclusive J/ψ production cross sec- tion is dσ/dy = 5.64 ± 0.22(stat.) ± 0.33(syst.) ± 0.12(lumi.) μb. The p T-differential cross section d2 σ/dp Tdy is measured in the p T range 0–10 GeV/c and compared with state-of- the-art QCD calculations. The J/ψ 〈p T〉 and $$ \left\langle {p}_{\mathrm{T}}^2\right\rangle $$ p T 2 are extracted and compared with results obtained at other collision energies.