Dynamical Generation of Yukawa Interactions in Intersecting D-brane Models

TL;DR

This paper presents a toy model in string theory where Yukawa couplings for quark and lepton masses are dynamically generated through interactions among preons and confinement dynamics, illustrating a new mechanism for mass generation.

Contribution

It introduces a supersymmetric composite model in type IIA string theory that naturally produces four generations and hierarchical Yukawa couplings via a novel dynamical mechanism.

Findings

Four generations of quarks and leptons emerge as composite fields.

Hierarchical Yukawa couplings are generated by string interactions and preon confinement.

The model serves as a proof of concept for dynamical Yukawa coupling generation.

Abstract

We construct a supersymmetric composite model in type IIA T^6/(Z_2 x Z_2) orientifold with intersecting D6-branes. Four generations of quarks and leptons are naturally emerged as composite fields at low energies. Two pairs of light electroweak Higgs doublets are also naturally obtained. The hierarchical Yukawa couplings for the quark-lepton masses can be generated by the interplay between the string-level higher dimensional interactions among "preons" and the dynamics of the confinement of "preons". Besides having four generations of quarks and leptons, the model is not realistic in some points: some exotic particles, one additional U(1) gauge symmetry, no explicit mechanism for supersymmetry breaking, and so on. This model is a toy model to illustrate a new mechanism of dynamical generation of Yukawa couplings for the masses and mixings of quarks and leptons.