Impact of bosonic decays on the search for t̃1 and b̃1 squarks

We perform a detailed study of the decays of the lighter top and bottom squarks (t̃1 and b̃1) in the Minimal Supersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons, i.e., t̃1→b̃1+(H+ or W+) and b̃1→t̃1+(H− or W−), can be dominant in a wide range of the MSSM parameters due to the large Yukawa couplings and mixings of t̃ and b̃. Compared to the decays into fermions, such as t̃1→t+(χ̃0i or g̃) and t̃1→b+χ̃+j, these bosonic decay modes can have significantly different decay distributions. We also show that the effect of the supersymmetric QCD running of the quark and squark parameters on the t̃1 and b̃1 decay branching ratios is quite dramatic. These could have an important impact on the search for t̃1 and b̃1 and the determination of the MSSM parameters at future colliders.