Neutrino Masses, Mixing Angles and the Unification of Couplings in the MSSM

TL;DR

This paper re-examines gauge and Yukawa coupling unification in the MSSM considering recent neutrino oscillation evidence, highlighting the role of large lepton mixing and its impact on unification parameters.

Contribution

It demonstrates that large lepton mixing allows Yukawa unification at intermediate tanβ values, providing new insights into GUT model structures.

Findings

Yukawa unification is possible for intermediate tanβ with large lepton mixing.

Lepton mixing influences the favored high-energy mass matrix structures.

Yukawa unification can serve as a probe for GUT models.

Abstract

In the light of the gathering evidence for $\nu_{\mu}-\nu_{\tau}$ neutrino oscillations, coming in particular from the Super-Kamiokande data on atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa couplings within the minimal supersymmetric extension of the Standard Model (MSSM). Guided by a range of different grand-unified models, we stress the relevance of large mixing in the lepton sector for the question of bottom-tau Yukawa coupling unification. We also discuss the dependence of the favoured value of $\tan\beta$ on the characteristics of the high-energy quark and lepton mass matrices. In particular, we find that, in the presence of large lepton mixing, Yukawa unification can be achieved for intermediate values of $\tan\beta$ that were previously disfavoured. The renormalization-group sensitivity to the structures of different mass matrices may enable Yukawa unification to serve as a useful probe of GUT models.