Supersymmetric scenarios with dominant radiative neutralino decay

The radiative decay of the next-to-lightest neutralino into a lightest neutralino and a photon is analyzed in the minimal supersymmetric standard model. We find that significant regions of the supersymmetric parameter space with large radiative branching ratios (up to about 100%) do exist. The radiative channel turns out to be enhanced when the neutralino tree-level decays are suppressed either open-quotes kinematically close-quote close-quote or open-quotes dynamically.close-quote close-quote In general, in the regions allowed by data from CERN LEP and not characterized by asymptotic values of the supersymmetric parameters, the radiative enhancement requires tanβ≅1 and/or M1≅M2, and negative values of μ. We present typical scenarios where these conditions are satisfied, relaxing the usual relation M1=(5)/(3)tan2θWM2, i.e., gaugino mass unification at the grand unified theory scale. The influence of varying the top-squark masses and mixing angle when the radiative decay is enhanced is also considered. Some phenomenological consequences of the above picture are discussed. copyright 1997 The American Physical Society