Measurement of exclusive Υ photoproduction from protons in p Pb collisions at √sNN=5.02TeV

The exclusive photoproduction of Υ (nS) meson states from protons, γp→Υ(nS)p (with n = 1 , 2 , 3), is studied in ultraperipheral p Pb collisions at a centre-of-mass energy per nucleon pair of sNN=5.02TeV. The measurement is performed using the Υ (nS) → μ⁺μ^- decay mode, with data collected by the CMS experiment corresponding to an integrated luminosity of 32.6nb-1. Differential cross sections as functions of the Υ (nS) transverse momentum squared pT2, and rapidity y, are presented. The Υ (1 S) photoproduction cross section is extracted in the rapidity range | y| < 2.2 , which corresponds to photon–proton centre-of-mass energies in the range 91<Wγp<826GeV. The data are compared to theoretical predictions based on perturbative quantum chromodynamics and to previous measurements.