Fractionally Charged Particles as Evidence for Supersymmetry

Supersymmetric grand unified models with fractionally charged color singlets ("fractons") are considered. It is shown that the minimal supersymmetrized fracton model, which occurs in SU(7), gives a value of ${sin}^2\theta \left(m_W\right)$ that is naturally lower than the minimal SU(5) supersymmetric grand unified theory prediction, and can be in agreement with experiment for fracton charge $q=\frac{e}{3}$.