Charged-fermion masses in SO(10)SO(10): Analysis with scalars in 10⊕12010⊕120

We consider the scenario in which the mass matrices of the charged fermions in the SO(10)SO(10) grand unified theory are generated exclusively by renormalizable Yukawa couplings to one 10⊕12010⊕120 representation of scalars. We analyze, partly analytically and partly numerically, this scenario in the three-generations case. We demonstrate that it leads to unification of the b and τ   masses at the GUT scale. Testing this scenario against the mass values at the GUT scale, obtained from the renormalization-group evolution in the minimal SUSY extension of the Standard Model, we find that it is not viable: either the down-quark mass or the top-quark mass must be unrealistically low. If we include the CKM mixing angles in the test, then, in order that the mixing angles are well reproduced, either the top-quark mass or the strange-quark mass together with the down-quark mass must be very low. We conclude that, assuming a SUSY SO(10)SO(10) scenario, charged-fermion mass generation based exclusively on one 10⊕12010⊕120 representation of scalars is in contradiction with experiment.