BOSONIC DECAYS OF (T)OVER-TILDE(2) AND (B)OVER-TILDE(2)

We perform a detailed study of the decays of the heavier top and botto m squarks ((t) over tilde(2) and (b) over tilde(2)) in the Minimal Sup ersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons, i.e. (t) over tilde(2) --> (t) over tilde(1) + (h(0), H-0,A(0) or Z(0)), (t) over tilde(2) --> (b) over tilde(1,2) + (H+ or W+), and the analogous (b) over tilde(2) decays, can be dominant in a wide range of the model parameters due to the large Yukawa couplings a nd mixings of t and b. Compared to the conventional decays into fermio ns, such as (t) over tilde(2) --> t + (<(chi)over tilde>(0)(i) or (g) over tilde) and (t) over tilde(2) --> b + <(chi)over tilde>(+)(j), the se bosonic decay modes can have significantly different decay structur es and distributions. This could have an important impact on the searc h for (t) over tilde(2) and (b) over tilde(2) and the determination of the MSSM parameters at future colliders. (C) 1998 Elsevier Science B. V. All rights reserved.