Thrust distribution in Higgs decays at the next-to-leading order and beyond

Abstract

We present predictions for the thrust distribution in hadronic decays of the Higgs boson at the next-to-leading order and the approximate next-to-next-to-leading order. The approximate NNLO corrections are derived from a factorization formula in the soft/collinear phase-space regions. We find large corrections, especially for the gluon channel. The scale variations at the lowest orders tend to underestimate the genuine higher order contributions. The results of this paper is therefore necessary to control the perturbative uncertainties of the theoretical predictions. We also discuss on possible improvements to our results, such as a soft-gluon resummation for the 2-jets limit, and an exact next-to-next-to-leading order calculation for the multi-jets region.

Resummed predictions for hadronic Higgs boson decays

“…In a recent publication [26], the distributions of the thrust variable in these decay processes were considered and fixed-order computations up to approximate NNLO (which contribute at O(α 3 s ) relative to a Born H → bb/gg process) were performed. In that work, the authors noted the poor convergence of the perturbative series for both processes and were able to show that the approximate NNLO corrections obtained from the singular terms of a SCET-derived factorisation formula could ameliorate the scale dependence of the calculations.…”

“…Here, we provide resummed predictions at NNLL accuracy which complement the results of ref. [26]. Compared to NNLL, the resummation at NNLL accuracy incorporates the complete O(α 2 s ) singular structure for T 2 → 0, i.e.…”

“…The ingredients necessary for NNLL accuracy are all available in the literature and many have been compiled in ref. [26]. For the H → bb case, we take the hard function from ref.…”

“…For the H → bb case, we take the hard function from ref. [26]. Since we are considering only massless b-quarks, we can use the soft and jet functions as implemented in ref.…”

“…Because of the resummation of large logarithms of τ , our results provide a physical description at small τ , as can be seen in figure 1, improving on the resummed-expanded results presented in ref. [26]. However, the range of validity of the resummed calculation is still limited to low τ values, since the factorisation formula we rely on (eq.…”