Search for the photoproduction of the η0-Meson

Abstract

An attempt has been made to detect the photoproduction of the η0 by observation of recoil protons at fixed momentum and angle from the reaction γ+p→+p+η0. The yield as a function of bremsstrahlung peak energy should exhibit an abrupt increase as the incident peak energy becomes sufficient to produce the η0 in coincidence with the observed recoil proton. Measurements were made every 25 MeV with 1% accuracy from below the single-pion threshold to about 1100 MeV at a 35° proton angle and at three proton momenta (420, 550 and 638 MeV/c). No steps in the excitation function were seen; in particular, a statistical analysis sets upper limits of about 0.5 μb/sr at each of the three proton momenta for the photoproduction of a mass 550 MeV particle. The over-all shapes of the curves (apart from the single-pion production) are consistent with the phase space for double-pion production.