Measurement of the Λ→n+γ branching ratio

The branching ratio for the \ensuremath{\Lambda} weak radiative decay has been measured to be B(\ensuremath{\Lambda}\ensuremath{\rightarrow}n+\ensuremath{\gamma})/(\ensuremath{\Lambda}\ensuremath{\rightarrow}anything) =[1.78\ifmmode\pm\else\textpm\fi{}0.24(stat)${\ifmmode\pm\else\textpm\fi{}}_{0.16}^{0.14}$(syst)]\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$. A low-energy kaon beam was used to produce the \ensuremath{\Lambda} hyperons via the reaction ${\mathit{K}}^{\mathrm{\ensuremath{-}}}$+p\ensuremath{\rightarrow}\ensuremath{\Lambda}+${\mathrm{\ensuremath{\pi}}}^{0}$ at rest. Photons from the signal channel and ${\mathrm{\ensuremath{\pi}}}^{0}$ decay were detected with a NaI(Tl) array. The final spectrum contains 287 events after background subtraction, an order of magnitude more events than from the only previous measurement.