The differential crosssection as a function of rapidity has been measured for the exclusive production of $J/\psi$ and $\psi(2S)$ mesons in protonproton collisions at $\sqrt{s}=7$ TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb$^{1}$. The crosssections 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 nexttoleading order QCD predictions as well as with models that include saturation effects.
Feynman diagrams displaying (a) exclusive $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ and (b) inelastic $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ production where a small number of additional particles are produced due to gluon radiation and (c),(d) proton dissociation. Equivalent diagrams apply for $\psi {(2S)}$ production. 
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% Acceptance for (solid) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ and (dotted) $\psi {(2S)}$ decays as a function of their rapidity. 
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% Invariant mass distribution of muon pairs after the selection requirements. The horizontally hatched regions show the $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ (left) signal and (right) sideband regions. The diagonally hatched regions show the $\psi {(2S)}$ (left) signal and (right) sideband regions. The data are fitted (solid curve) with Crystal Ball functions for the signals and an exponential function for the nonresonant background; the latter contribution is shown by the dashed curve. 
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% Transverse momentum squared distributions for (a) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ and (b) $\psi {(2S)}$ candidates, where the nonresonant background contribution has been subtracted using sidebands. The points are data, the solid curve is the total fit while the different contributions are as described. 
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% Differential crosssection for (a) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ and (b) $\psi {(2S)}$ production compared to LO and NLO predictions of [5]. The band indicates the total uncertainty, most of which is correlated between bins. 
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% Photoproduction crosssection as a function of the centreofmass of the photonproton system with the powerlaw fit from [8] superimposed. The LHCb data points for $W_+(W_)$ are derived assuming the powerlaw fit for $W_(W_+)$. The uncertainties are correlated between bins. Fixed target results are from the E401 [33], E516 [34] and E687 [35] collaborations. 
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% Differential distribution for (a) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ and (b) $\psi {(2S)}$ compared to the predictions of Gay Ducati, Griep and Machado [3] and Motyka and Watt [2], which include saturation effects. The points are data where the error bars indicate the uncorrelated uncertainties. The band indicates the total uncertainty, most of which is correlated between bins. 
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Animated gif made out of all figures. 
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% Quantities entering the crosssection calculations as a function of meson rapidity. 
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% Differential crosssection times branching ratio, in units of $\rm pb$ , for mesons decaying to two muons, both with $2.0<\eta<4.5$, in bins of meson rapidity. Only the uncorrelated statistical uncertainties are quoted with the central values. The uncertainties, correlated between bins, are tabulated in the lower table. Those with an asterisk enter into the systematic uncertainty. 
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% Fraction of events in a given meson rapidity range where both muons have $2.0<\eta<4.5$. 
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% Comparison of this result to various theoretical predictions. 
Table_4.pdf [43 KiB] HiDef png [74 KiB] Thumbnail [38 KiB] tex code 
Created on 14 October 2019.