Supersymmetric electroweak corrections to bottom squark decay into a lighter top squark and charged Higgs boson

The Yukawa corrections of order O(αewmt(b)2/mW2), O(αewmt(b)3/mW3), and O(αewmt(b)4/mW4) to the width of bottom squark decay into a lighter top squark plus a charged Higgs boson are calculated in the minimal supersymmetric standard model. These corrections depend on the masses of the charged Higgs boson and lighter top squark and the parameters tan β and μ. For favorable parameter values, the corrections decrease or increase the decay widths significantly. In particular, for high values of tan β (=30) the corrections exceed 10% for both b-tilde1 and b-tilde2 decay. But for low values of tan β (=4,10) the corrections are small and the magnitudes are less than 10%. The numerical calculations also show that using the running bottom quark mass, which includes the QCD effects and resums all high order (tan β)-enhanced effects can vastly improve the convergence of the perturbation expansion