The reaction γp → ϱOp at 5.5 to 18 GeV

Abstract

The reaction γp→ ϱ O p in the energy range 5.5< Eγ<18 GeV was studied using a streamer chamber exposed to an 18 GeV bremsstrahlung beam. Our results differ from earlier counter experiments in the following ways: (i) the ϱ cross section is constant (≈ 12 μb) throughout the energy range and (ii) both dσ dt |t min and the slope parameter of dσ dt are constant and have significantly smaller values ( ≈82 μ b GeV 2 and 6.6 GeV −2 respectively ) at all our energies. The t-dependence of the ϱ density matrix in both s− and t-channel helicity frames shows that the production conserves the s-channel helicity at all t-values observed (up to −0.8 GeV 2).