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Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector

The DELPHI Collaboration·J. Abdallah
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Abstract

Inclusive J/psi production in photon-photon collisions has been observed at LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an integrated luminosity of 617 pb^{-1}, yielding a cross-section of sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the event shapes of different types of gamma gamma processes in the PYTHIA program, we conclude that (74 +/- 22)% of the observed J/psi events are due to `resolved' photons, the dominant contribution of which is most probably due to the gluon content of the photon.

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The DELPHI Collaboration, J. Abdallah. 2003-07-17. Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector. https://doi.org/10.1016/s0370-2693(03)00660-9

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