On the two-loop decoupling corrections to tau-lepton and b-quark running masses in the MSSM

TL;DR

This paper calculates two-loop decoupling corrections to tau-lepton and b-quark masses in the MSSM, focusing on Yukawa and strong interaction effects, which are crucial for precise parameter determination in beyond Standard Model theories.

Contribution

It provides the first calculation of NNLO Yukawa corrections to fermion masses in the MSSM, extending previous work on strong interaction corrections.

Findings

Yukawa corrections significantly affect fermion mass relations at large tan beta.

The combined strong and Yukawa corrections are essential for accurate mass predictions.

Tau-lepton corrections serve as a good approximation to the full two-loop results.

Abstract

Masses of heavy Standard Model fermions (top-quark, bottom-quark, and tau-lepton) play an important role in the analysis of theories beyond the SM. They serve as low-energy input and reduce the parameter space of such theories. In this paper Minimal supersymmetric extension of the SM is considered and two-loop relations between known SM values of fermion masses and running parameters of the MSSM are studied within the effective theory approach. Both b-quark and tau-lepton have the same quantum numbers with respect to SU(2) groupand in the MSSM acquire their masses due to interactions with the same Higgs doublet. As a consequence, for large values of tan beta parameter corresponding Yukawa couplings also become large and together with tan beta can significantly enhance radiative corrections. In the case of b-quark two-loop O(alpha_s^2) contribution to the relation between running bottom-quark mass in QCD and MSSM is known in literature. This paper is devoted to calculation of the NNLO corrections proportional to Yukawa couplings. For the tau-lepton obtained contribution can be considered as a good approximation to the full two-loop result. For the b-quark numerical analysis given in the paper shows that only the sum of strong and Yukawa corrections can play such a role.