Realistic Yukawa Structures from Orientifold Compactifications

TL;DR

This paper systematically analyzes D-brane quivers in string theory compactifications to identify configurations that produce realistic Yukawa couplings and neutrino masses, addressing the challenge of forbidden couplings due to global symmetries.

Contribution

It provides a comprehensive analysis of conditions under which D-brane instantons induce realistic Yukawa couplings without phenomenological issues.

Findings

Few quivers allow for realistic Yukawa structures.

Instantons can generate missing couplings without violating phenomenological constraints.

Only a small subset of models matches experimental observations.

Abstract

We perform a systematic analysis of globally consistent D-brane quivers which realize the MSSM, and analyze them with respect to their Yukawa couplings. Often, desired couplings are perturbatively forbidden due to the presence of global U(1) symmetries. We investigate the conditions under which D-brane instantons will induce these missing couplings without generating other phenomenological drawbacks, such as R-parity violating couplings or a mu-term which is too large. Furthermore, we systematically analyze which quivers allow for a mechanism that can account for the small neutrino masses and other experimentally observed hierarchies. We show that only a small fraction of the globally consistent D-brane quivers exhibits phenomenology compatible with experimental observations.