Two-loop supersymmetric QCD corrections to Higgs-quark-quark couplings in the generic MSSM

In this article we compute the two-loop supersymmetric QCD corrections to Higgs-quark-quark couplings in the generic minimal supersymmetric standard model (MSSM) generated by diagrams involving squarks and gluinos. We give analytic results for the two-loop contributions in the limit of vanishing external momenta for general supersymmetry (SUSY) masses valid in the MSSM with general flavor structure. Working in the decoupling limit (M-SUSY >> v) we resum all chirally enhanced corrections (related to Higgs-quark-quark couplings) up to order alpha((n+1))(s)tan(n) beta. This resummation allows for a more precise determination of the Yukawa coupling and Cabibbo-Kobayashi-Maskawa elements of the MSSM superpotential necessary for the study of Yukawa coupling unification. The knowledge of the Yukawa couplings of the MSSM superpotential in addition allows us to derive the effective Higgs-quark-quark couplings entering flavor changing neutral current processes. These effective vertices can in addition be used for the calculation of Higgs decays into quarks as long as M-SUSY > M-Higgs holds. Furthermore, our calculation is also necessary for consistently including the chirally enhanced self-energy contributions into the calculation of flavor changing neutral current processes in the MSSM beyond leading order. At two-loop order, we find an enhancement of the supersymmetry threshold corrections, induced by the quark self-energies, of approximately 9% for mu = M-SUSY compared to the one-loop result. At the same time, the matching scale dependence of the effective Higgs-quark-quark couplings is significantly reduced. DOI: 10.1103/PhysRevD.87.015013