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arXiv · 1002.3663

The Limits of Custodial Symmetry

R. Sekhar Chivukula·Stefano Di Chiara·Roshan Foadi·Elizabeth H. Simmons
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Abstract

We introduce a toy model implementing the proposal of using a custodial symmetry to protect the Z b_L bbar_L 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 in the top-quark mass generating sector. 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.

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R. Sekhar Chivukula, Stefano Di Chiara, Roshan Foadi, Elizabeth H. Simmons. 2010-02-19. The Limits of Custodial Symmetry. https://doi.org/10.1142/9789814329521_0013

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