New GUT predictions for quark and lepton mass ratios confronted with phenomenology

Abstract

Group theoretical factors from grand unified theory (GUT) symmetry breaking can lead to predictions for the ratios of quark and lepton masses (or Yukawa couplings) at the unification scale. Because of supersymmetric (SUSY) threshold corrections the viability of such predictions can depend strongly on the SUSY parameters. For three common minimal SUSY breaking scenarios with anomaly, gauge, and gravity mediation we investigate which GUT scale ratios ${m}_{e}/{m}_{d}$, ${m}_{\ensuremath{\mu}}/{m}_{s}$, ${y}_{\ensuremath{\tau}}/{y}_{b}$, and ${y}_{t}/{y}_{b}$ are allowed when phenomenological constraints from electroweak precision observables, $B$ physics, $(g\ensuremath{-}2{)}_{\ensuremath{\mu}}$, mass limits on sparticles from direct searches as well as, optionally, dark matter constraints are taken into account. We derive possible new predictions for the GUT scale mass ratios and compare them with the phenomenologically allowed ranges. We find that new GUT scale predictions such as ${m}_{\ensuremath{\mu}}/{m}_{s}=9/2$ or 6 and ${y}_{\ensuremath{\tau}}/{y}_{b}=3/2$ or 2 are often favored compared to the ubiquitous relations ${m}_{\ensuremath{\mu}}/{m}_{s}=3$ or ${y}_{\ensuremath{\tau}}/{y}_{b}=1$. They are viable for characteristic SUSY scenarios, testable at the CERN LHC and future colliders.