Improved supersymmetric QCD corrections to Higgs boson decays into quarks and squarks

Abstract

We improve the calculation of the supersymmetric $\mathcal{O}({\ensuremath{\alpha}}_{s})$ QCD corrections to the decays of Higgs bosons into quarks and squarks in the minimal supersymmetric standard model. In the on-shell renormalization scheme these corrections can be very large, which makes the perturbative expansion unreliable. This is especially serious for decays into bottom quarks and squarks for large $\mathrm{tan}\ensuremath{\beta}.$ Their corrected widths can even become negative. We show that this problem can be solved by a careful choice of the tree-level Higgs boson couplings to quarks and squarks, in terms of the QCD and SUSY QCD running quark masses, running trilinear couplings ${A}_{q},$ and on-shell left-right mixing angles of squarks. We also present numerical results for the corrected partial decay widths for the large $\mathrm{tan}\ensuremath{\beta}$ case.