Anomaly-free chiral fermion sets and gauge coupling unification

peer reviewedIn this work we search for minimal sets of chiral fermions, with arbitrary quantum numbers, beyond the Standard Model that are anomaly-free and lead to vector-like particles under SU(3) and U(1)_em after symmetry breaking. We further study which of these anomaly free sets lead to unification of the gauge couplings at energy scales higher that 5.0×10^15 GeV in order to be consistent with proton decay bounds. A similar study is performed in the context of the SU(5) gauge group; for some of the anomaly-free sets found it is possible to obtain unification of the gauge couplings with the extra fermions decoupling at high intermediate scales