Two-loop contributions to electroweak precision observables in the MSSM

TL;DR

This paper calculates two-loop MSSM contributions to electroweak precision observables, showing significant effects especially with strong squark mixing, and confirms small theoretical uncertainties across renormalization schemes.

Contribution

It provides detailed calculations of two-loop MSSM contributions to M_W and s_w^eff, including the Higgs mass M_h, with analysis of scheme dependence and numerical impact.

Findings

Contributions can be sizeable, especially with strong squark mixing.

Theoretical uncertainties are small across different renormalization schemes.

The Higgs mass M_h is retained accurately despite the gauge-less limit.

Abstract

The evaluation of the two-loop MSSM-contributions to the electroweak precision observables M_W and s_w^eff at order(alpha_t^2), order(alpha_t alpha_b), order(alpha_b^2) is presented. These contributions enter via Delta(rho), and it is explained in detail how one can retain the true, non-vanishing value of the MSSM Higgs boson mass M_h in spite of using the gauge-less limit in the calculation. The numerical results can be sizeable, in particular for strong squark mixing. By comparing the results in the on-shell and DR-bar renormalization schemes, the remaining theoretical uncertainty is found to be small.