1. The Limits of Custodial Symmetry
- Author
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Sekhar Chivukula, R, Foadi, Roshan, Simmons, Elizabeth H, and Di Chiara, Stefano
- Subjects
hep-ph - Abstract
We introduce a toy model implementing the proposal of using a custodialsymmetry to protect the Z b_L bbar_L coupling from large corrections. This"doublet-extended standard model" adds a weak doublet of fermions (including aheavy partner of the top quark) to the particle content of the standard modelin order to implement an O(4) x U(1)_X = SU(2)_L x SU(2)_R x P_LR x U(1)_Xsymmetry in the top-quark mass generating sector. This symmetry is softlybroken to the gauged SU(2)_L x U(1)_Y electroweak symmetry by a Dirac mass Mfor the new doublet; adjusting the value of M allows us to explore the range ofpossibilities between the O(4)-symmetric (M to 0) and standard-model-like (M toinfinity) limits.
- Published
- 2011