Non-minimal Higgs content in standard-like models from D-branes at a Z_N singularity

TL;DR

Constructing standard-like models from D-branes at Z_N singularities inherently leads to non-minimal Higgs sectors, causing flavor-changing neutral current issues, with specific bounds on Higgs doublets related to quark singlet counts.

Contribution

Demonstrates that all D-brane models at Z_N singularities inherently require non-minimal Higgs content, revealing a fundamental limitation in such constructions.

Findings

Lower bound on Higgs doublets tied to quark singlet number

Non-minimal Higgs content causes flavor-changing neutral currents

Constraints differ between orbifold and orientifold models

Abstract

We show that attempts to construct the standard model, or the MSSM, by placing D3-branes and D7-branes at a Z_N orbifold or orientifold singularity all require that the electroweak Higgs content is non-minimal. For the orbifold the lower bound on the number n(H) + n({\bar{H}}) of electroweak Higgs doublets is the number n(q^c_L)=6 of quark singlets, and for the orientifold the lower bound can be one less. As a consequence there is a generic flavour changing neutral current problem in such models.