Measurement of the ratio of prompt $\ddot{I}{‡}_c$ to $J/\ddot{I}ˆ$ production in $pp$ collisions at $\sqrt{s}=7$ TeV

Abstract

The prompt production of charmonium $\ddot{I}{‡}_c$ and $J/\ddot{I}ˆ$ states is studied in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the Large Hadron Collider. The $\ddot{I}{‡}_c$ and $J/\ddot{I}ˆ$ mesons are identified through their decays $\ddot{I}{‡}_c\to J/\ddot{I}ˆ{\hat{I}}^3$ and $J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}$ using 36 pb${}^{-1}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for $\ddot{I}{‡}_c$ and $J/\ddot{I}ˆ$, $\ddot{I}ƒ(\ddot{I}{‡}_c\to J/\ddot{I}ˆ{\hat{I}}^3)/\ddot{I}ƒ(J/\ddot{I}ˆ)$, is determined as a function of the $J/\ddot{I}ˆ$ transverse momentum in the range $2<p_{\mathrm{T}}^{J/\ddot{I}ˆ}<15$ GeV/$c$. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low $p_{\mathrm{T}}^{J/\ddot{I}ˆ}$ region.

Published version