Search for Sub-threshold Photoproduction of J/Psi Mesons

A search was made for sub-threshold $J\mathrm{/}\psi$ 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.