  Consider 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 $(\Sigma^+, \Sigma^0, \Sigma^-)$, which corresponds to the proposal of
hep-ph/0112232. This disproves the assertion that the latter is somehow a
``trivial'' or ``expected'' discovery.
