Precise predictions for Higgs physics in supersymmetric models

Abstract

In the Minimal Supersymmetric Standard Model (MSSM), the mass of the SM-like Higgs boson can be predicted in terms of the model parameters and therefore used as a precision observable to constrain the MSSM parameter space. The precise prediction of the lightest MSSM Higgs boson mass in scenarios with one or several heavy supersymmetric particles requires the resummation of higher-order logarithmic contributions obtained within an effective-field-theory (EFT) approach. By combining the EFT calculation with a fixed-order calculation, a precise prediction also for low and intermediary SUSY scales can be obtained. This method is called the hybrid approach and is implemented, for instance, in the publicly available code FeynHiggs.We discuss various improvements to this hybrid framework. First, we consider the resummation of logarithmic contributions proportional to the bottom-Yukawa coupling, including two-loop $\Delta_b$-resummation. For large $\tan\beta$, this can lead to large upward shifts of the Higgs mass compared to the existing fixed-order calculations. Second, we improve the implemented EFT calculation by fully taking into account the effect of the phases of complex soft SUSY-breaking parameters. In addition, we discuss the inclusion of partial N$^3$LL resummation.After that, we turn to the case when there is a significant hierarchy between the gluino mass and the masses of the scalar top quarks. In such a situation, the current Higgs boson mass predictions so far have suffered from large theoretical uncertainties related to non-decoupling power-enhanced gluino contributions in the EFT employing the $\overline{\text{DR}}$ renormalization scheme. We demonstrate that the theoretical predictions in the heavy gluino region are vastly improved by the introduction of a more suitable renormalization scheme for the EFT calculation. It is shown that within this scheme, the large gluino contributions are absorbed into the model parameters, resulting in reliable and numerically stable predictions in the heavy-gluino region.The presented improvements will become publicly available as parts of FeynHiggs.