Exclusive J/ψ and ψ(2S) production in pp collisions at √s= 7 TeV

Abstract

Exclusive J/ψ and ψ(2S) vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between 2.0 and 4.5 are measured to be σpp→J/ψ(→μ+μ−)(2.0 < ημ± < 4.5) = 307 ± 21 ± 36 pb, σpp→ψ(2S)(→μ+μ−)(2.0 < ημ± < 4.5) = 7.8 ± 1.3 ± 1.0 pb, where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The J/ψ photoproduction cross-section has been measured as a function of the photon-proton centre-ofmass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction crosssection.