Fractional-charge hadrons and leptons to tell the Standard Model group apart

The gauge group of strong and electroweak interactions in Nature could be any of the four that share the same Lie algebra, SU(3)c× SU(2)L× U(1)Y/Zₚ≡ Gₚ with Zₚ=₆,Z₃,Z₂,Z₁\. Each of these cases allows in its spectrum for the matter fields of the SM but also for new distinctive representations, e.g. under the assumption that qL possesses the minimum possible hypercharge in Nature, Gₚ allows for particles with a multiple of $p\,e/6$ for electric charge. This letter discusses how these new possibilities in the spectrum could be used to tell the SM group apart.