Gauge-coupling-constant magnitudes in the Pati-Salam model

A doubly tiered hierarchy of symmetry breaking is proposed in which a unified gauge group is broken first to the Pati-Salam group SU(2)L×SU(2)R×SU(4), subsequently to the SU(2)L×U(1)×SU(3)c group containing the known elementary-particle interactions. The second level of symmetry breaking corresponds to the differentiation of baryon number from lepton number. Such a hierarchy is consistent with the phenomenology of the Pati-Salam model for integrally charged quarks. The proposed hierarchy allows the weak angle to remain in the range 3/8≤sin²θW≤0.42 as the quark-gluon coupling constant becomes appropriately large. It is suggested that the first level of symmetry breaking corresponds to the separation of gravity from elementary-particle interactions. The hierarchy is also shown to apply for fractionally charged quarks, increasing the quark-gluon coupling constant αₛ≈0.1 while leaving the weak angle sin²θW≈3/8.