Higgs boson decay to massive bottom quarks at order $\alpha_s^4$ induced by top-quark Yukawa couplings

TL;DR

This paper calculates the impact of top-quark Yukawa couplings on the Higgs decay to bottom quarks at high order, refining theoretical predictions to match future experimental precision.

Contribution

It provides the first $ ext{O}( ext{α}_s^4)$ calculation of top-Yukawa induced contributions to Higgs decay into massive bottom quarks.

Findings

Top-Yukawa contributions increase decay width by 0.4%.

Results reduce theoretical scale dependence to 0.4%.

Enhancements are significant for future collider measurements.

Abstract

The Higgs boson decay to massive bottom quarks has the largest branching ratio. The decay is mainly induced by the bottom-quark Yukawa coupling with the decay rate calculated up to $\mathcal{O}(\alpha_s^4)$ assuming the massless final-state bottom quark. The top-quark Yukawa coupling induced contribution starts at $\mathcal{O}(\alpha_s^2)$, and exhibits logarithmic and power enhancements, making the perturbative expansion converge slowly. We present a calculation of such contributions at $\mathcal{O}(\alpha_s^4)$ to the decay into massive bottom quarks in which the squared amplitudes contain two top-quark Yukawa couplings. We find that they increase the decay width, relative to the result up to $\mathcal{O}(\alpha_s^3)$, by $0.4\%$, larger than the experimental precision at future lepton colliders, and reduce the scale dependence significantly down to $0.4\%$.