S. Ambrosanio et B. Mele, SUPERSYMMETRIC SCENARIOS WITH DOMINANT RADIATIVE NEUTRALINO DECAY, Physical review. D. Particles and fields, 55(3), 1997, pp. 1399-1417
The radiative decay of the next-to-lightest neutralino into a lightest
neutralino and a photon is analyzed in the minimal supersymmetric sta
ndard model. We find that significant regions of the supersymmetric pa
rameter space with large radiative branching ratios (up to about 100%)
do exist. The radiative channel turns out to be enhanced when the neu
tralino tree-level decays are suppressed either ''kinematically'' or '
'dynamically.'' In general, in the regions allowed by data from CERN L
EP and not characterized by asymptotic values of the supersymmetric pa
rameters, the radiative enhancement requires tan beta similar or equal
to 1 and/or M(1) similar or equal to M(2), and negative values of mu.
We present typical scenarios where these conditions are satisfied, re
laxing the usual relation m(1)=5/3 tan(2) theta(w)M(2)i.e., gaugino ma
ss unification at the grand unified theory scale. The influence of var
ying the top-squark masses and mixing angle when the radiative decay i
s enhanced is also considered. Some phenomenological consequences of t
he above picture are discussed.