Measurement of the 2-photon production of ρ0ω with the JADE detector at PETRA

With the JADE detector the 2-photon production of the vector-meson pair ωρ0 was studied. The measurement with an integrated luminosity of 224 (pb)-1 was performed at a mean beam energy of 18 GeV. Both the cross section σsub(γγ→ωπ+π-) in dependence on the γγ c.m. energy Wγγ and for Wγγ>1.5 GeV the contribution with intermediate ρ0 production to this cross section were determined. For smaller γγ energies no ρ0 contribution could be determined, because this range lies below the threshold for ωρ0 and no from the phase space distinguishable ρ0 signal in the invariant π+π- mass occurs. But in this range the measured cross section σsub(γγ→ωπ+π-) is extensively exhausted by the expected contribution of the reaction γγ→a2(1320)→ωπ+π-. The increase of the cross section σsub(γγ→ωπ+π-) indicated by ARGUS and TPC/γγ in the Wγγ range around 1.9 GeV cannot be confirmed in this measurement. In this range the cross section measured in this analysis lies significantly below the measurements of these experiments, while in the remaining Wγγ range all three measurements agree within the errors. The comparison of the measured cross section with the t-channel factorization model and the qanti qqanti q model shows that both models are able to describe the data. The increase of the cross section around 1.9 GeV in the measurements of ARGUS and TPC/γγ however leads to discrepancies in comparison to these models. (orig.)