Neutrino masses, mixing angles and the unification of couplings in the MSSM

Abstract

In the light of the gathering evidence for ν µ − ν τ 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 β 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 β 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.

Fixed points in the evolution of neutrino mixings

“…(17) or eqs. (19)(20)(21) is the existence of fixed points at U ab = 0. The character of the fixed points (UV or IR) and the rate of approaching them depend on the mass factors A ab .…”

“…Large number of papers addressed the issue of theoretical explanation of neutrino masses and mixings and of incorporating it into some global solution to the flavour problem [11,12,13,14,15,16,17,18,19,20,21,22]. One attractive possibility for giving the three flavours of neutrinos small Majorana masses is the seesaw mechanism which generates in the effective low energy theory (MSSM or the SM) a dimension five operator.…”

Electroweak baryogenesis in supersymmetric variants

“…A detailed analysis can be found in ref. [14,15]. The originally found two-stage PT [11] at even smaller m stopR including a color-breaking phase seems to be excluded because in this case one never would return to the Higgs phase [16].…”

“…In the MSSM one can have explicit CP-violating phases in the µ and A top parameter [5,14], in the NMSSM there are even more possibilities. They are restricted by the experimental bound on the neutron electric dipole moment.…”

“…In the SM we have CP-violation in the KM-matrix, but this is a very small effect. In "Beyond" models like the MSSM there are more possiblities, but the size of such effects is still under discussion [5,14]. (iii) One needs nonequilibrium.…”