We consider the possibility that R-parity violating interactions of particles which do not involve the first generation have large (up to 1) coupling constants, λ. Such couplings, if they exist, could have a number of phenomenological consequences: renormalization of the b - τ mass ratio, generation of ντ mass in the MeV region, etc. In grand unified models, where B- and L-violating couplings appear simultaneously, proton decay can be forbidden in virtue of the hierarchical flavor structure of λ. However, due to Cabibbo-Kobayashi-Maskawa mixing this decay is induced already at one loop. Present experimental data give the upper bound λ ⪅ 10 -8 (or | λ' λ″| ⪅ 7 × 10 -16, on products of certain L- and B-violating coupling constants, in a more general context). The bound can be avoided if there is an asymmetry between the L- and B-violating couplings of the usual matter fields. In the SU(5) model the asymmetry can be related to the doublet-triplet splitting.
Nuclear Physics B
- Pub Date:
- February 1996
- High Energy Physics - Phenomenology
- Version published after revision. A discussion of the pattern of the sneutrino vacuum expectation values has been added