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Observation of charmonium pairs produced exclusively in $pp$ collisions

Abstract : A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of $3{\rm\ fb}^{-1}$ collected at centre-of-mass energies of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges $(-3.5,-1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measured to be $$ \begin{array}{rl} \sigma^{J/\psi J/\psi} &= 58\pm10{(\rm stat)} \pm 6{(\rm syst)} {\rm\ pb} , \\ \sigma^{J/\psi\psi(2S)} &= 63 ^{+27}_{-18}{(\rm stat)}\pm 10{(\rm syst)} {\rm\ pb} , \\ \sigma^{\psi(2S)\psi(2S)} &< 237 {\rm\ pb}, \\ \sigma^{\chi_{c0}\chi_{c0}} &< 69 {\rm\ nb}, \\ \sigma^{\chi_{c1}\chi_{c1}} &< 45 {\rm\ pb}, \\ \sigma^{\chi_{c2}\chi_{c2}} &< 141 {\rm\ pb}, \\ \end{array} $$ where the upper limits are set at the 90% confidence level. The measured $J/\psi J/\psi$ and $J/\psi\psi(2S)$ cross-sections are consistent with theoretical expectations.
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http://hal.in2p3.fr/in2p3-01038113
Contributor : Sabine Starita <>
Submitted on : Wednesday, July 23, 2014 - 11:55:01 AM
Last modification on : Friday, November 20, 2020 - 3:30:14 PM

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R. Aaij, Y. Amhis, S. Barsuk, M. Borsato, O. Callot, et al.. Observation of charmonium pairs produced exclusively in $pp$ collisions. Journal of Physics G Nuclear Physics, Institute of Physics (IOP), 2014, 41, pp.115002. ⟨10.1088/0954-3899/41/11/115002⟩. ⟨in2p3-01038113⟩

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