# Central exclusive production of $J/\psi$ and $\psi(2S)$ mesons in pp collisions at $\sqrt s$ = 13 TeV

LHCb Collaboration; Bernet, R; Müller, K; Serra, N; Steinkamp, O; Straumann, U; Vollhardt, A; et al (2018). Central exclusive production of $J/\psi$ and $\psi(2S)$ mesons in pp collisions at $\sqrt s$ = 13 TeV. Journal of High Energy Physics, 10:167.

## Abstract

Measurements are reported of the central exclusive production of J/ψ and ψ(2S) mesons in pp collisions at a centre-of-mass energy of 13 TeV. Backgrounds are significantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross-sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2.0 < η < 4.5, are measured to be
$\begin{array}{c} {\sigma}_{J/\psi \to {\mu}^{+}{\mu}^{-}} = 435 \pm 18 \pm 11 \pm 17\ \mathrm{p}\mathrm{b}\\ {}{\sigma}_{\psi (2S)\to {\mu}^{+}{\mu}^{-}} = 11.1 \pm 1.1 \pm 0.3 \pm 0.4\ \mathrm{p}\mathrm{b}. \end{array}$
The first uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross-sections are also measured differentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross-sections are derived and compared to previous experiments, and a deviation from a pure power-law extrapolation of lower energy data is observed.

## Abstract

Measurements are reported of the central exclusive production of J/ψ and ψ(2S) mesons in pp collisions at a centre-of-mass energy of 13 TeV. Backgrounds are significantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross-sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2.0 < η < 4.5, are measured to be
$\begin{array}{c} {\sigma}_{J/\psi \to {\mu}^{+}{\mu}^{-}} = 435 \pm 18 \pm 11 \pm 17\ \mathrm{p}\mathrm{b}\\ {}{\sigma}_{\psi (2S)\to {\mu}^{+}{\mu}^{-}} = 11.1 \pm 1.1 \pm 0.3 \pm 0.4\ \mathrm{p}\mathrm{b}. \end{array}$
The first uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross-sections are also measured differentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross-sections are derived and compared to previous experiments, and a deviation from a pure power-law extrapolation of lower energy data is observed.

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