The SU(3)_C * SU(4)_W * U(1)_{B-L} Models with Left-Right Unification

TL;DR

This paper explores a partial unification model based on SU(4)_W*U(1)_{B-L} that can break down to the left-right model via Higgs or orbifold mechanisms, analyzing phenomenology, anomaly cancellation, and unification prospects.

Contribution

It compares four-dimensional Higgs breaking and five-dimensional orbifold breaking of the SU(4)_W*U(1)_{B-L} model, highlighting the advantages of orbifold outer automorphism for anomaly freedom and phenomenological implications.

Findings

Orbifold breaking with outer automorphism avoids U(1)_Z anomaly.

Mirror fermions persist at low energy and mix with SM fermions.

Gauge coupling unification and grand unification prospects are discussed.

Abstract

The left-right models provide an explanation for the parity asymmetry in the Standard Model (SM). To further understand the origin of the left-right symmetry, we study a partial unification model based on SU(4)_W*U(1)_{B-L} which can be broken down to the minimal left-right model either through the Higgs mechanism in four dimensions or through the five-dimensional orbifold gauge symmetry breaking with inner or outer automorphism. We scrutinize all these breaking mechanisms and find that for the orbifold breaking in five dimensions, the rank-reducing outer automorphism is better than the inner automorphism and can make the low energy theory free of the U(1)_Z anomaly. For the four-dimensional model with the Higgs mechanism, we study in detail both its structure and its typical phenomenology. It turns out that this four-dimensional scenario may predict some new phenomenology since the new mirror fermions (which are introduced in order to fill the SM fermions into SU(4)_W without anomaly) are preserved at low energy scale and mix with the SM fermions. We also examine the gauge coupling unification in each case, and discuss the possibility for unifying this partial unification group with the Pati-Salam group SU(4)_{PS} to realize a grand unification.