Study of ψ (2 S ) production and cold nuclear matter effects in p Pb collisions at √(s_N N)=5 TeV

The production of ψ (2 S ) mesons is studied in dimuon final states using proton-lead ( p Pb) collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of 1 . 6 nb −1 . The nucleon-nucleon centre-of-mass energy of the p Pb collisions is √(s_N N)=5 TeV. The measurement is performed using ψ (2 S ) mesons with transverse momentum less than 14 GeV/ c and rapidity y in the ranges 1 . 5 < y < 4 . 0 and −5 . 0 < y < −2 . 5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for ψ (2 S ) mesons. Using the production cross-section results of ψ (2 S ) and J/ψ mesons from b -hadron decays, the bb cross-section in p Pb collisions at √(s_N N)=5 TeV is obtained.