Measurement of theπ−p→nγDifferential Cross Section Near the Roper Resonance,P11(1460)

We measured six differential cross sections for ${\pi }^{-}p\to n\gamma$ at 490-MeV/c incident ${\pi }^{-}$ momentum. Our data do not agree with recent theoretical predictions. We find no evidence, in the sense suggested by Donnachie, for the classification of the Roper resonance, $P_{11}\mathrm{}\left(1460\right)\mathrm{}$, in an SU(3) antidecuplet. Our angular distribution is consistent with the classification of the Roper resonance in an octet, as predicted by the simplest quark models. Using detailed balance, our results agree well with the reported cross sections for the inverse reaction, which are deduced from $\gamma d$ data.