Production of χc2 mesons in photon-photon collisions at LEP

Abstract

We present an observation at LEP of the production of χ c2 mesons in the collisions of two quasi-real photons using the OPAL detector. The χ c2 mesons are reconstructed in the decay channel χ c2 →J/ψ γ→ℓ + ℓ − γ (with ℓ = e, μ) using all data taken at e +e − centre-of-mass energies of 91 and 183 GeV, corresponding to integrated luminosities of 167 and 55 pb −1 respectively. The two-photon width of the χ c2 is determined to be Γ( χ c2→ γγ)=1.76±0.47±0.37±0.15 keV, where the first error is statistical, the second is systematic and the third comes from branching ratio uncertainties.