Branching Ratio of the Electromagnetic Decay of the Sigma⁺(1385)

The CLAS detector was used to obtain the first ever measurement of the electromagnetic decay of the $\Sigma^{*+}(1385)$ from the reaction $\gamma p \to K^0 \Sigma^{*+}(1385)$. A real photon beam with a maximum energy of 3.8 GeV was incident on a liquid-hydrogen target, resulting in the photoproduction of the kaon and $\Sigma^*$ hyperon. Kinematic fitting was used to separate the reaction channel from the background processes. The fitting algorithm exploited a new method to kinematically fit neutrons in the CLAS detector, leading to the partial width measurement of $250.0\pm56.9(stat)^{+34.3}_{-41.2}(sys)$ keV. A U-spin symmetry test using the SU(3) flavor-multiplet representation yields predictions for the $\Sigma^{*+}(1385)\to\Sigma^{+}\gamma$ and $\Sigma^{*0}(1385)\to\Lambda\gamma$ partial widths that agree with the experimental measurements.