Prompt production of charmonium $\chi_{ c0}$, $\chi_{ c1}$ and $\chi_{ c2}$ mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of $\sqrt{ s}=7$TeV. The $\chi_{ c}$ mesons are identified through their decay to $J/\psi\gamma$, with $J/\psi\to\mu^+\mu^-$ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of $1.0\mathrm{ fb}^{ -1}$ collected by the LHCb detector, is used to measure the relative prompt production rate of $\chi_{ c1}$ and $\chi_{ c2}$ in the rapidity range $2.0<y<4.5$ as a function of the $J/\psi$ transverse momentum from 3 to 20 GeV$/c$. First evidence for $\chi_{ c0}$ meson production at a high-energy hadron collider is also presented.
Categories: hep-ex
