New paths through the desert: Improving on minimal SU(5)

Abstract

We present a model with a particle spectrum identical to minimal SU(5) below the SU(5)-breaking mass scale $M_X$, where the gauge group is the standard ${\mathrm{SU}}_C\mathrm{}\left(3\right)\mathrm{}\times {\left[{\mathrm{SU}}_L\mathrm{}\right(2)\mathrm{}\times \mathrm{U}\mathrm{}(1\left)\right]}_{\mathrm{GWS}}$ (GWS= Glashow-Weinberg-Salam). However, unlike minimal SU(5), a nonstandard hypercharge embedding into ${\mathrm{E}}_6$ allows our model to have $M_X$ large enough to agree with present limits on proton decay and simultaneously have a weak mixing angle in agreement with the experimental value extracted from the $W$ and $Z^0$ masses.