The Photoproduction of  ⁰Mesons in Hydrogen

Accurate absolute differential cross sections for the reaction γ + p → π0 + p have been measured at 90° in the centre-of-mass system at 22 energies between 200 and 300 MeV for the incident photons by counting the protons at laboratory angles of 36° and 40.5° in the laboratory system. The protons were emitted from a thin hydrogen target exposed to the bremsstrahlen beam of the Glasgow synchrotron. The measurements agree with previously measured values at 200 and 300 MeV, but are about 30% lower near 250 MeV. The results have been compared with dispersion relation calculations.