Beautiful mirrors for a pNGB Higgs

TL;DR

This paper explores models where the Higgs is a pseudo Nambu-Goldstone boson, introducing bottom partners to address the Zbb coupling discrepancy, and predicts new light custodial particles with rich phenomenology.

Contribution

It introduces bottom partners in specific SO(5) representations to improve the fit to Zbb couplings in pNGB Higgs models, expanding the phenomenological implications.

Findings

Bottom partners improve Zbb coupling fits.

Large Zb_Rb_R shift predicts light custodians.

Tree-level corrections dominate one-loop estimates.

Abstract

We consider one of the most significant deviations from the Standard Model: the forward-backward asymmetry of the b-quark measured at leptonic colliders. We investigate the possibility to solve this discrepancy by introducing new physics at the TeV scale. We focus on models where the Higgs is a pseudo Nambu-Goldstone boson of a new strongly coupled sector with a global SO(5) symmetry broken spontaneously to SO(4). Besides the usual top partners, we introduce bottom partners in the representations 16 and 4 of SO(5) and show that they can improve significantly the fit by correcting the Zbb couplings. We also estimate the corrections to the couplings at one-loop and obtain that the tree-level ones dominate and can give a reliable estimation. We find that the large shift required for Zb_Rb_R leads to light custodians associated to the b-quark, similar to the top partners, as well as a rich phenomenology involving neutral interactions in the bottom-sector.