HIGGS SCALAR-PSEUDOSCALAR MIXING IN THE MINIMAL SUPERSYMMETRIC STANDARD MODEL

In the minimal supersymmetric Standard Model, the heaviest CP-even Hig gs boson H and the CP-odd Higgs scalar A are predicted to be almost de generate in mass at the tree level, for the wide kinematic range M-A > 2M(Z) and tan beta greater than or equal to 2. However, if large soft -CP-violating Yukawa interactions involving scalar quarks of the third generation are present in the theory, then the CP invariance of the H iggs potential can be maximally broken beyond the Born approximation, and the high degree of mass degeneracy between H and A may be lifted t hrough a sizeable HA mixing. After taking the CP-odd tadpole renormali zation of the A boson into account, we find that the small mass differ ence M-H - M-A, which is about 1% of the A-boson mass at the tree leve l, can be substantially enhanced to the 25% level at the one-loop orde r. We also find that the loop-induced mixing between the lightest CP-e ven Higgs boson h and the A boson may be of comparable size to M-A. We briefly discuss the main phenomenological implications of the predict ed hA and HA mixings for the general Higgs-boson mass spectrum and for CP-violating observables at collider and lower energies. (C) 1998 Els evier Science B.V. All rights reserved.