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

The Yukawa corrections of order O(alpha(pw)m(t(b))(2)/m(W)(2)), O(alpha(ew)m(t(b))(3)/m(W)(3)), and O(alpha(ew)m(t(b))(4)/m(W)(4)) 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 beta and mu. For favorable parameter values, the corrections decrease or increase the decay widths significantly. In particular, for high values of tan beta (= 30) the corrections exceed 10% for both (b) over tilde (1) and (b) over tilde (2) decay. But for low values of tan beta (=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 beta)-enhanced effects can vastly improve the convergence of the perturbation expansion.