Measurement of pion-proton bremsstrahlung for pions at 299 MeV

We have measured the fivefold differential cross section $d^5$σ/d${\Omega }_{\pi }$d${\Omega }_{\gamma }$ ${\mathrm{dE}}_{\gamma }$ for the process ${\pi }^{+}$p→${\pi }^{+}$pγ with incident pions of energy 299 MeV. The angular regions for the outgoing pions (55°≤${\theta }_{\mathrm{lab}{}^{\pi }\mathrm{\le }95}$°), and photons (${\theta }_{\mathrm{lab}{}^{\gamma }=241\mathrm{}\mathrm{°}\pm 10}$°) in coplanar geometry are selected to maximize the sensitivity to the radiation from the magnetic dipole moment of the ${\Delta }^{++}$(1232) resonance. At low photon energies, the data agree with the soft-photon approximation to pion-proton bremsstrahlung. At forward pion angles the data agree with older data and with the latest theoretical calculations for 2.3${\mu }_p$≤${\mu }_{\Delta }$≤3.3${\mu }_p$. However at more backward pion angles where no data existed, the predictions fail.