Measurement of sigma(chic2)/ sigma(chic1) at sqrt(s) = 7 TeV

A measurement of the relative prompt production rate of $\chi_{c2}$ and $\chi_{c1}$ with 4.62 fb$^{-1}$ of data collected at LHC at $\sqrt{s}= 7 {TeV}$ is presented. The two states are measured via their radiative decays $ \chi_c \rightarrow J/\psi + \gamma$, with the photon converting into an $e^+e^-$ pair in the tracking detector. The kinematic acceptance is defined by $|y(J/\psi)| < 1.0$ and $p_T(\gamma) > 0.5$~GeV$/c$. The measurement is given in six intervals of $p_T(J/\psi)$ between 7 and 25~GeV$/c$.