The Limits of Custodial Symmetry
Abstract
We introduce a toy model implementing the proposal of using a custodial symmetry to protect the Zbb coupling from large corrections. This "doublet-extended standard model" adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4) x U(1)_X = SU(2)_L x SU(2)_R x P_{LR} x U(1)_X symmetry that protects the Zbb coupling. This symmetry is softly broken to the gauged SU(2)_L x U(1)_Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M to 0) and standard-model-like (M to infinity) limits.
Keywords
Cite
@article{arxiv.1009.2477,
title = {The Limits of Custodial Symmetry},
author = {R. Sekhar Chivukula and Stefano Di Chiara and Roshan Foadi and Elizabeth H. Simmons},
journal= {arXiv preprint arXiv:1009.2477},
year = {2010}
}
Comments
4 pages, 2 included eps figures. Talk presented by RSC at 22nd Recontres de Blois, July 15-20, 2010