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.
Highlights
With the original vacuum and can trigger EWSB
We find that the large shift required for ZbRbR 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
To be able to generate the top mass by partial compositeness and trigger EWSB we introduce an operator OSqtCFT in a representation of SO(5), we use the index qt to distinguish it from the one involved in the generation of the bottom mass that has index qb
Summary
The spectrum of heavy vectors arising from this diagonalization is slightly modified with respect to the original mass, but the corrections are small as long as tθ ≡ g0/gρ ≪ 1, as was assumed to be the case. The masses of the composite fields that do not mix with the elementary ones remain unchanged. The masses of the fermions corresponding to the orthogonal combinations become mΨ = mΨ 1 + t2θΨ.. The mass matrices can be diagonalized straightforward numerically, it is worth obtaining the analytic diagonalization expanding in some small parameter By this procedure one can obtain analytic expressions for the couplings in the mass basis and understand the size and sign of the corrections as functions of the fundamental parameters of the theory. In the subsection we will show our results for the Zbb interactions using this perturbative diagonalization
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