Branching ratio of the electromagnetic decay of theΣ+(1385)

Abstract

The CLAS detector was used to obtain the first ever measurement of the electromagnetic decay of the ${\ensuremath{\Sigma}}^{*+}(1385)$ from the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\Sigma}}^{*+}(1385)$. 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 ${\ensuremath{\Sigma}}^{*}$ 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 measured decay widths ratio ${\ensuremath{\Sigma}}^{+}(1385)\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{+}\ensuremath{\gamma}/{\ensuremath{\Sigma}}^{+}(1385)\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{+}{\ensuremath{\pi}}^{0}=11.95\ifmmode\pm\else\textpm\fi{}2.21(\mathrm{stat}{)}_{\ensuremath{-}1.21}^{+0.53}(\mathrm{sys})%$ and a deduced partial width of $250.0\ifmmode\pm\else\textpm\fi{}56.9(\mathrm{stat}{)}_{\ensuremath{-}41.2}^{+34.3}(\mathrm{sys})\text{ }\text{ }\mathrm{keV}$. A U-spin symmetry test using the SU(3) flavor-multiplet representation yields predictions for the ${\ensuremath{\Sigma}}^{*+}(1385)\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{+}\ensuremath{\gamma}$ and ${\ensuremath{\Sigma}}^{*0}(1385)\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma}$ partial widths that agree with the experimental measurements.