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Free keywords:
High Energy Physics - Experiment, hep-ex
MPINP:
LHCb - Abteilung Hofmann
Abstract:
The differential cross-section as a function of rapidity has been measured
for the exclusive production of $J/\psi$ and $\psi(2S)$ 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 $$\begin{array}{rl} \sigma_{pp\rightarrow
J/\psi\rightarrow{\mu^+}{\mu^-}}(2.0<\eta_{\mu^\pm }<4.5)=&291\pm 7\pm19 {\rm \
pb},\\
\sigma_{pp\rightarrow\psi(2S)\rightarrow{\mu^+}{\mu^-}}(2.0<\eta_{\mu^\pm}<4.5)=&6.5\pm
0.9\pm 0.4 {\rm \ pb},\end{array}$$ 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.
