Solving local anomaly equations in gauge-rank extensions of the standard model

Abstract

We consider local (or perturbative) gauge anomalies in models which extend the rank of the Standard Model (SM) gauge group and the chiral fermion content only by n SM singlets. We give a general solution to the anomaly cancellation conditions (ACCs) of an additional U(1) subgroup for the ACCs that involve only SM fermions and we examine whether a corresponding solution exists for the remaining ACCs. We show that a solution to the remaining ACCs always exists for n≥5 in the family-nonuniversal case or n≥3 in the family-universal case. In the special case where only a single family carries nonvanishing charges, we find a general solution to all ACCs, for any value of n.