Abstract
Inclusive J/ψ production in photon–photon collisions has been observed at LEP II beam energies. A clear signal from the reaction γγ→J/ψ+X is seen. The number of observed N(J/ψ→μ+μ−) events is 36±7 for an integrated luminosity of 617 pb−1, yielding a cross-section of σ(J/ψ+X)=45±9(stat)±17(syst) pb. Based on a study of the event shapes of different types of γγ processes in the PYTHIA program, we conclude that (74±22)% of the observed J/ψ events are due to ‘resolved’ photons, the dominant contribution of which is most probably due to the gluon content of the photon.
Highlights
An important component of the e+e− collisions at LEP II energy is the two-photon fusion process
We present the J /ψ production characteristics together with the PYTHIA predictions
We have studied the inclusive J /ψ production from γ γ collisions
Summary
An important component of the e+e− collisions at LEP II energy is the two-photon fusion process. It has been pointed out that two-photon production of inclusive J /ψ mesons: e+ + e− → e+ + e− + γ1 + γ2,. The first process is described by the vector-meson dominance (VDM) model [2]: γ1 → c + c, γ2 → q + q,. Inclusive J /ψ production in γ γ processes: (a) through vector-meson dominance, (b) via gluon content of the photon, i.e., ‘resolved’ contributions. It is seen that this process requires production of a ‘resolved’ gluon (gγ ) from both photons. The purpose of this Letter is to report the observation of inclusive J /ψ production from the two-photon fusion process, to give its production characteristics along with the cross-section and to assess the relative importance of the production processes discussed above. The measurement of inclusive J /ψ production in the μ+μ− channel and its interpretation in terms of diffractive and resolved processes is presented in Section 3 followed by a summary and conclusions
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