ΣRadiative Decay and the Angular Momentum ofΣPionic Decay

Abstract

We have studied the pion spectrum in the ${\Sigma }^{\pm }\to n+{\pi }^{\pm }+\gamma$ decay in order to determine the angular-momentum channel of the $\Sigma$ pionic decay. We discuss the results from measurements of a sample of 14 800 ${\Sigma }^{+}\to {\pi }^{+}+n$ decays and 25 000 ${\Sigma }^{-}\to {\pi }^{-}+n$ decays. After subtraction of the background, we find 26 ${\Sigma }^{+}$ radiative decays and 28 ${\Sigma }^{-}$ radiative decays with $P_{\mathrm{c}.\mathrm{m}.\mathrm{}}<166\mathrm{}$ MeV/c. The combination ${\Sigma }^{+}\to {\pi }^{+}+n$ decays via $P$ wave and ${\Sigma }^{-}\to {\pi }^{-}+n$ decays via $S$ wave is 45 times more likely than the combination ${\Sigma }^{+}\to {\pi }^{+}+n$ decays via $S$ wave and ${\Sigma }^{-}\to {\pi }^{-}+n$ decays via $P$ wave. This means that our result is 2.7 standard deviations in favor of the first combination.