Residual effects of heavy sparticles in the bottom quark Yukawa coupling: A comparative study for the MSSM and NMSSM

If the sparticles are relatively heavy (a few TeV) while the Higgs sector is not so heavy (m(A) is not so large), the Higgs boson Yukawa couplings can harbor sizable quantum effects of sparticles and these large residual effects may play a special role in probing supersymmetry at foreseeable colliders. In this work, focusing on the supersymmetric QCD effects in the hb (b) over bar coupling (h is the lightest CP-even Higgs boson), we give a comparative study for the two popular supersymmetric models: the MSSM and NMSSM. While for both models the supersymmetric QCD can leave over large residual quantum effects in hb (b) over bar coupling, the NMSSM can allow for a much broader region of such effects. Since these residual effects can be over 20% for the hb (b) over bar coupling (and thus over 40% for the ratio Br(h -> b (b) over bar)/Br(h -> tau(+)tau(-))), future measurements may unravel the effects of heavy sparticles or even distinguish the two models. (C) 2009 Elsevier B.V. All rights reserved.