DECAYS OF THE K- P ATOM AND THE LAMBDA(1405)

To investigate differences between some recent calculations on the decays of the K- p atom, we calculate the pionic decays K- p --> LAMBDA-pi-0, SIGMA+pi-, SIGMA-0-pi-0, and SIGMA-pi+ in an isobar model and compare them with experimental rates determined from measured branching ratios together with the imaginary part of the KNBAR scattering amplitude. The comparison shows that the coupling constants at the strong-interaction vertices are reduced significantly from the on-shell values. These coupling constants are then applied to an isobar-model calculation of the radiative transition rates. Comparing these with results from a recent experiment gives values for the radiative decay widths of the LAMBDA(1405): GAMMA-LAMBDA(1405)--> LAMBDA-gamma = 27 +/- 8 keV and GAMMA-LAMBDA-(1405)--> SIGMA-0-gamma = 10 +/- 4 or 23 +/- 7 keV.