Infra-red fixed point structure characterising SUSY SU(5) symmetry breaking

Infra - red stability of Yukawa and soft - breaking fixed points

We investigate the infra-red stability of the fixed points in the evolution of the Yukawa couplings, A-parameters and soft scalar masses in a broad class of supersymmetric theories. We show that the issue of stability is essentially determined in all three cases by the eigenvalues of the same matrix. In a very wide range of physically interesting theories it follows that, in the asymptotically ...

The Quasi-Infra-Red Fixed Point at Higher Loops

We calculate the four-loop β-function for the generalised Wess-Zumino model. We use the result and Padé-Borel summation to discuss the domain of attraction of the quasi-infra-red fixed point of the top-quark Yukawa coupling in the supersymmetric standard model, and argue that the domain is in fact substantial.

Aspects of SUSY and R-Symmetry Breaking

Soft SUSY breaking and family symmetry

A spontaneously broken non-Abelian SU(3) family symmetry can generate a realistic form for quark, charged lepton and neutrino masses and mixing angles. It also gives a new solution to the SUSY flavour problem by ensuring near family degeneracy of the soft mass SUSY breaking terms. However the need to generate large third generation fermion masses means that the group must be strongly broken to ...

Infra-red fixed points in supersymmetry

The Standard Model (SM) is a great success in describing the strong and electroweak interactions based on an underlying gauge principle, but one of its main weaknesses is that the masses of the matter particles, the quarks and leptons, are free parameters of the theory. This weakness persists in the Minimal Supersymmetric Standard Model (MSSM). The fermions mass problem in the MSSM arises from ...