Higgs boson decay to massive bottom quarks at order αₛ⁴ induced by top-quark Yukawa couplings

A bstract 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 O(αₛ⁴) O α s 4 assuming the massless final-state bottom quark. The top-quark Yukawa coupling induced contribution starts at O(αₛ²) O α s 2 , and exhibits logarithmic and power enhancements, making the perturbative expansion converge slowly, which is a feature not present in the hadronic Higgs boson decay. We present a calculation of such contributions at O(αₛ⁴) O α s 4 to the decay into massive bottom quarks in which the squared amplitudes contain two top-quark Yukawa couplings and the final state must include at least a bottom quark pair. We find that they increase the decay width, relative to the result up to O(αₛ³) O α s 3 , by 0 . 4%, larger than the experimental precision at future lepton colliders, and reduce the scale dependence significantly down to 0 . 4%.