Nondecoupling of Heavy Fermions and a Special Yukawa Texture

TL;DR

This paper demonstrates that new physics involving an isosinglet vector-like quark can preserve certain Yukawa texture zero patterns despite stringent experimental constraints, due to nondecoupling effects.

Contribution

It reveals that nondecoupling of heavy vector-like quarks can maintain specific Yukawa textures, challenging the expectation that heavy new physics decouples at high energies.

Findings

Nondecoupling effects of heavy quarks can influence Yukawa textures.

A four texture zero Yukawa ansatz remains viable with vector-like quark mixing.

Heavy vector-like quarks do not necessarily decouple, affecting flavor physics.

Abstract

Talk based on work entitled ``Yukawa textures, new physics and nondecoupling,'' done in collaboration with G. C. Branco and J. I. Silva-Marcos, arXiv:hep-ph/0612252, to appear in Phys. Rev. D. In this work we pointed out that New Physics can play an important r\^ ole in rescuing some of the Yukawa texture zero ans\" atze which would otherwise be eliminated by the recent, more precise measurements of $V_{CKM}$. We have shown that the presence of an isosinglet vector-like quark which mixes with standard quarks, can render viable a particularly interesting four texture zero Yukawa ansatz. The crucial point is the nondecoupling of the effects of the isosinglet quark, even for arbitrary large values of its mass.