Phenomenological analysis of D-brane Pati-Salam vacua

TL;DR

This paper analyzes low-energy Pati-Salam models derived from D-branes, addressing matter-Higgs mixing issues, proposing solutions for Higgs mass protection, and exploring stringy instanton effects on fermion masses.

Contribution

It introduces a D-brane setup that separates matter and Higgs fields to solve mixing problems and examines mechanisms to protect Higgs components from heavy masses.

Findings

Separation of matter and Higgs fields in D-brane intersections reduces mixing issues.

A splitting mechanism can protect Higgs from large mass terms.

Stringy instantons can generate missing Yukawa couplings and influence fermion mass textures.

Abstract

In the present work we perform a phenomenological analysis of the effective low energy models with Pati-Salam (PS) gauge symmetry derived in the context of D-branes. A main issue in these models arises from the fact that the right-handed fermions and the PS-symmetry breaking Higgs field transform identically under the PS symmetry, causing unnatural matter-Higgs mixing effects. We argue that this problem could be solved in particular D-brane setups where these fields arise in different intersections. We further observe that whenever a large Higgs mass term is generated in a particular class of mass spectra, a splitting mechanism -reminiscent of the doublet triplet splitting- may protect the neutral Higgs components from a heavy mass term. We analyze the implications of each individual representation which in principle is available in these models in order to specify the minimal spectrum required to build up a consistent PS model which reconciles the low energy data. A short discussion is devoted on the effects of stringy instanton corrections, particularly those generating missing Yukawa couplings and contributing to the fermion mass textures. We discuss the correlations of the intersecting D-brane spectra with those obtained from Gepner constructions and analyze the superpotential, the resulting mass textures and the low energy implications of some examples of the latter along the lines proposed above.