Measurement of the $\psi(2S)$ production cross-section at $\sqrt{s}$=7TeV in LHCb

The inclusive production of $\psi(2S)$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$=7 TeV is studied using the LHCb detector. The differential cross-section is measured as a function of the $\psi(2S)$ transverse momentum and rapidity. The data sample corresponds to about $35$ pb$^{-1}$ integrated luminosity collected between April and November 2010 at the Large Hadron Collider. The inclusive $\psi(2S)$ (from $b-$decay and promptly produced) are reconstructed in two decay modes: $\psi(2S) \rightarrow \mu^+ \mu^-$ and $\psi(2S) \rightarrow J/\psi (\mu\mu) \pi^+ \pi^-$; we measure, respectively: \begin{eqnarray*} \sigma(0<\p_T\leq12~{\rm GeV}/c, 2<y\leq4.5) &=& 1.88 \pm 0.02 \pm 0.31^{+0.25}_{-0.48} ~~{\rm \mu b} \\ \sigma(3<\p_T\leq16~{\rm GeV}/c, 2<y\leq4.5) &=& 0.62 \pm 0.04 \pm 0.12^{+0.07}_{-0.14} ~~{\rm \mu b} \end{eqnarray*} where the first uncertainty is statistical, the second is systematic and the third error is the uncertainty due to the unknown polarisation.