B-d,s(0)->mu(-)mu(+) decay in the MSSM - art. no. 054012

We present the results of the complete one-loop computation of the B-d,s(o) -->l(+)l(-) decay rate in the MSSM. Both sources of the FCNC, the CKM matri x and off-diagonal entries of the sfermion mass matrices are considered. St rong enhancement of the branching ratio (compared to the SM prediction) can be obtained in the large tan beta similar tom(t)/m(b) regime in which the neutral Higgs boson "penguin" diagrams dominate. We make explicit the stron g dependence of this enhancement on the top squarks mixing angle in the cas e of the chargino contribution and on the mu parameter in the case of the g luino contribution. We show that, in some regions of the MSSM parameter spa ce. the branching ratio for this process can be as Large as 10(-(5-4)) resp ecting all existing constraints. including the CLEO measurement of BR(B-->X (s)gamma). We also estimate that for chargino and top squark masses similar to O(100 GeV) BR(B-s(o)-->l(+)l'(-)) with ll' = e tau or mu tau can be of the order of 10(-11) for the still allowed values of the off-diagonal entri es id the slepton mass matrix.