Measurement of Radiative Pion-Proton Scattering near theΔ(1236)Resonance

Abstract

We have measured the differential cross section for radiative ${\pi }^{+}$ -proton scattering, ${\pi }^{+}p\to {\pi }^{+}p\gamma$, at 294 MeV under kinematical conditions favorable to the observation of radiation from the magnetic dipole moment of the ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ resonance. For radiated photon energies above 30 MeV, our data do not agree with explicit theoretical calculations which include an estimate of the magnetic moment radiation. Rather, our data agree with the simple expression in the c.m. system, $\frac{d\sigma }{d{\tilde{\Omega }}_{\pi }d{\tilde{\Omega }}_{\gamma }d{\tilde{E}}_{\gamma }}=\frac{{\sigma }_0}{{\tilde{E}}_{\gamma }}$, over the full range of photon energy, up to ${\tilde{E}}_{\gamma }=140\mathrm{}$ MeV. Preliminary measurements of radiative ${\pi }^{-}$ -proton scattering have also been made.