Updated measurements of exclusive $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(2S)$ production cross-sections in $pp$ collisions at $\sqrt{s}=7$ TeV

Abstract

The differential cross-section as a function of rapidity has been measured for the exclusive production of $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(2S)$ mesons in proton-proton collisions at $\sqrt{s}=7$ TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb${}^{-1}$. The cross-sections times branching fractions to two muons having pseudorapidities between 2.0 and 4.5 are measured to be $$\begin{array}{rl}\ddot{I}{ƒ}_{pp\to J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}}(2.0<\hat{I}{\cdot }_{\hat{I}{¼}^{\pm }}<4.5)=& 291\pm 7\pm 19\mathrm{pb},\\ \ddot{I}{ƒ}_{pp\to \ddot{I}ˆ(2S)\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}}(2.0<\hat{I}{\cdot }_{\hat{I}{¼}^{\pm }}<4.5)=& 6.5\pm 0.9\pm 0.4\mathrm{pb},\end{array}$$ where the first uncertainty is statistical and the second is systematic. The measurements agree with next-to-leading order QCD predictions as well as with models that include saturation effects.

17 pages, 7 figures