Measurement of the relative rate of prompt Χc0, Χc1 and Χc2 production at √s = 7TeV

Prompt production of charmonium Χ _c0, Χ _c1 and Χ _c2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of √s = 7TeV. The Χ _c mesons are identified through their decay to J/Φ,γ with J/Φ → μ ⁺μ ^- using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0 fb ^-1 collected by the LHCb detector, is used to measure the relative prompt production rate of Χ _c1 and Χ _c2 in the rapidity range 2:0 < y < 4:5 as a function of the J/Φ transverse momentum from 3 to 20 GeV=c. First evidence for Χ _c0 meson production at a high-energy hadron collider is also presented.