Unification of gauge couplings and the tau neutrino mass in Supergravity without R-parity

TL;DR

This paper demonstrates that R-parity violation in supergravity models can naturally reconcile gauge coupling unification with observed tau neutrino masses, affecting the strong coupling constant prediction.

Contribution

It shows how R-parity violation impacts gauge coupling unification and the tau neutrino mass predictions within supergravity frameworks.

Findings

R-parity violation lowers the predicted alpha_s(M_Z) closer to experimental values.

The effect is linked to the two-loop b-quark Yukawa contributions in RG evolution.

A few percent change in alpha_s(M_Z) can occur with small tau neutrino masses.

Abstract

Minimal R-parity violating supergravity predicts a value for $alpha_s(M_Z)$ smaller than in the case with conserved R-parity, and therefore closer to the experimental world average. We show that the R-parity violating effect on the $alpha_s$ prediction comes from the larger two-loop b-quark Yukawa contribution to the renormalization group evolution of the gauge couplings which characterizes R-parity violating supergravity. The effect is correlated to the tau neutrino mass and is sensitive to the initial conditions on the soft supersymmetry breaking parameters at the unification scale. We show how a few percent effect on $alpha_s(M_Z)$ may naturally occur even with tau neutrino masses as small as indicated by the simplest neutrino oscillation interpretation of the atmospheric neutrino data from Super-Kamiokande.