Improved full one-loop corrections to A0 → (q)over-tilde1(q)over-tilde2 and (q)over-tilde2 → (q)over-tilde1 A0

We calculate the full electroweak one-loop corrections to the decay of the CP-odd Higgs boson A(0) into scalar quarks in the minimal supersymmetric extension of the Standard Model (MSSM). Due to the complex structure of the electroweak sector a proper renormalization of many parameters in the on-shell renormalization scheme is necessary. For the decay into sbottom quarks, especially for large tan beta, the corrections can be very large in the on-shell renormalization scheme, which makes the perturbation series unreliable. We solve this problem by an appropriate definition of the tree-level coupling in terms of running quark masses and running trilinear couplings A(q). We also discuss the decay of heavy scalar quarks into light scalar quarks and A(0). We find that the corrections are significant and therefore cannot be neglected. (C) 2003 Published by Elsevier B.V.