Impact of bosonic decays on the search for (t)over-tilde(1) and (b)over-tilde(1) squarks

We perform a detailed study of the decays of the lighter top and bottom squ arks (<(<tau>)over tilde>(1) and (b) over tilde (1)) in the Minimal Supersy mmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons, i.e., <(<tau>)over tilde>(1) --> (b) over tilde (1) + (H+ or W+) an d (b) over tilde (1) --> (t) over tilde (1) + (H- or W-), can be dominant i n a wide range of the MSSM parameters due to the large Yukawa couplings and mixings of (t) over tilde and (b) over tilde. Compared to the decays into fermions, such as (t) over tilde (1) --> t + (<(<chi>)over tilde>(0)(1) or (g) over tilde) and (t) over tilde (1) --> b +<(<chi>)over tilde>(+)(j), th ese bosonic decay modes can have significantly different decay distribution s. We also show that the effect of the supersymmetric QCD running of the qu ark and squark parameters on the ii and (b) over tilde (1) decay branching ratios is quite dramatic. These could have an important impact on the searc h for (t) over tilde (1) and (b) over tilde (1) and the determination of th e MSSM parameters at future colliders. (C) 2001 Published by Elsevier Scien ce B.V.