2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/41360Consider the addition of a right-handed SU(2) fermion multiplet (with neither color nor hypercharge) to each family of quarks and leptons. The resultant theory admits a new U(1) gauge symmetry only if the additional multiplet is a singlet $N_R$, which corresponds to the well-known case of $U(1)_{B-L}$, or a triplet $(Σ^+, Σ^0, Σ^-)$, which corresponds to the proposal of hep-ph/0112232. This disproves the assertion that the latter is somehow a ``trivial'' or ``expected'' discovery.The content of this paper is now part of hep-ph/0206150High Energy Physics - Phenomenologytext