Effective Yukawa couplings and flavor-changing Higgs boson decays at linear colliders

TL;DR

This paper explores how linear colliders can test a model where Higgs Yukawa couplings are radiatively generated, leading to enhanced flavor-changing decays and altered Higgs decay signatures, providing a way to probe new physics beyond the Standard Model.

Contribution

It demonstrates the potential of linear colliders to directly investigate radiative Yukawa coupling generation and flavor-changing Higgs decays, which are significantly enhanced compared to the Standard Model.

Findings

Enhanced Higgs decay into photons and gauge bosons for light Higgs.

Measurable branching ratio for H→bs decay (10^{-4} to 10^{-3}) for Higgs lighter than 140 GeV.

Detailed analysis of Higgs production cross sections and decay signatures at linear colliders.

Abstract

We analyze the advantages of a linear-collider program for testing a recent theoretical proposal where the Higgs-boson Yukawa couplings are radiatively generated, keeping unchanged the standard-model mechanism for electroweak-gauge-symmetry breaking. Fermion masses arise at a large energy scale through an unknown mechanism, and the standard model at the electroweak scale is regarded as an effective field theory. In this scenario, Higgs boson decays into photons and electroweak gauge-boson pairs are considerably enhanced for a light Higgs boson, which makes a signal observation at the LHC straightforward. On the other hand, the clean environment of a linear collider is required to directly probe the radiative fermionic sector of the Higgs boson couplings. Also, we show that the flavor-changing Higgs-boson decays are dramatically enhanced with respect to the standard model. In particular, we find a measurable branching ratio in the range (10^{-4}-10^{-3}) for the decay H\to bs for a Higgs boson lighter than 140 GeV, depending on the high-energy scale where Yukawa couplings vanish. We present a detailed analysis of the Higgs boson production cross sections at linear colliders for interesting decay signatures, as well as branching-ratio correlations for different flavor-conserving/nonconserving fermionic decays.