Search for sub-threshold photoproduction of J/ψ [J/psi] mesons

A search was made for sub-threshold J/ψ production from a carbon target using a mixed real and quasi-real Bremsstrahlung photon beam with an endpoint energy of 5.76 GeV. No events were observed, which is consistent with predictions assuming quasi-free production. The results place limits on exotic mechanisms that strongly enhance quasi-free production. PACS numbers: 13.60.Le,14.40.Gx,25.20.Lj