String scale unification in an SU(6)xSU(2) GUT

J. Rizos; K. Tamvakis

doi:10.1016/S0370-2693(97)01181-7

paper

String scale unification in an SU(6)xSU(2) GUT

arXiv:hep-ph/9702295 · doi:10.1016/S0370-2693(97)01181-7

Abstract

We construct and analyze an $S U (6) \times S U (2)$ GUT. The model is k=1 string embedable in the sense that we employ only chiral representations allowed at the k=1 level of the associated Kač-Moody Algebra. Both cases $S U (6) \times S U (2)_{L}$ and $S U (6) \times S U (2)_{R}$ are realized. The model is characterized by the $S U (6) \times S U (2) \to S U (4) \times S U (2) \times S U (2)$ breaking scale $M_{X}$ , and the $S U (4) \times S U (2) \times S U (2) \to S U (3)_{C} \times S U (2)_{L} \times U (1)_{Y}$ breaking scale $M_{R}$ . The spectrum bellow $M_{R}$ includes an extra pair of charge-1/3 colour-triplets of mass $M_{I} \leq M_{R}$ that does not couple to matter fields and, possibly, an extra pair of isodoublets. Above $M_{X}$ the SU(6) and SU(2) gauge couplings always unify at a scale which can be taken to be the string unification scale $M_{s} \sim 5 \times 1 0^{17} G e V$ . The model has Yukawa coupling unification since quarks and leptons obtain their masses from a single Yukawa coupling. Neutrinos obtain acceptably small masses through a see-saw mechanism. Coloured triplets that couple to matter fields are naturally split from the coexisting isodoublets without the need of any numerical fine tuning.

15 pages, Latex2e, three figures included, comments added, published version

String scale unification in an SU(6)xSU(2) GUT

Abstract

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