Angular distributions of pion-proton bremsstrahlung at 298 MeV

Abstract

We report new measurements of ${\pi }^{\pm }p\to {\pi }^{\pm }p\gamma$ at 18 photon angles for 298-MeV incident pions. At all angles, the photon spectrum falls monotonically with increasing $E_{\gamma }$ and lacks the predicted structure due to the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonance. The soft-photon approximation agrees with the data for $E_{\gamma }<50\mathrm{}$ MeV only. For higher $E_{\gamma }$, the simple external-emission-dominance calculation provides an acceptable but imperfect description of all results.