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Non-perturbaitve effects in Higgs boson decays to electroweak vector bosons and photons

Alexander Khodjamirian, Kirill Melnikov, Arkady Vainshtein

TL;DR

This work estimates leading non-perturbative QCD corrections to Higgs decays $H \to \gamma Z$ and $H \to \gamma \gamma$ arising from light-quark loops. Using a light-cone operator-product expansion, the twist-2 photon distribution amplitude, the quark condensate $\langle \bar q q \rangle$, and the magnetic susceptibility $\chi$, the authors quantify how these effects scale with the Higgs and vector-boson masses. They find that $H \to ZZ^*$ receives an extremely small non-perturbative correction (order ${\cal O}(10^{-12})$ relative to the leading amplitude), while $H \to \gamma Z$ and $H \to \gamma \gamma$ acquire corrections of order ${\cal O}(10^{-5})$, driven by long-distance fragmentation into photons. The results indicate that non-perturbative QCD effects will not hinder percent-level Higgs precision studies at the HL-LHC or future colliders, and they refine expectations in the ongoing debate about the size of these corrections.

Abstract

We estimate the magnitude of the leading non-perturbative QCD corrections to the decays of the Higgs boson to the $γZ$ and $γγ$ final states. These corrections originate from the light-quark contributions to such decays. We show that the non-perturbative effects are suppressed by the small Yukawa couplings of light quarks, but that there is no further quark-mass suppression. This is at variance with what is found in the standard perturbative calculations of the light-quark contributions. We demonstrate that the non-perturbative corrections modify the $H \to γZ$ and $H \to γγ$ decay rates by $O(10^{-5})$, well below the expected precision with which such decays can be studied both at the high-luminosity LHC and at future colliders.

Non-perturbaitve effects in Higgs boson decays to electroweak vector bosons and photons

TL;DR

This work estimates leading non-perturbative QCD corrections to Higgs decays and arising from light-quark loops. Using a light-cone operator-product expansion, the twist-2 photon distribution amplitude, the quark condensate , and the magnetic susceptibility , the authors quantify how these effects scale with the Higgs and vector-boson masses. They find that receives an extremely small non-perturbative correction (order relative to the leading amplitude), while and acquire corrections of order , driven by long-distance fragmentation into photons. The results indicate that non-perturbative QCD effects will not hinder percent-level Higgs precision studies at the HL-LHC or future colliders, and they refine expectations in the ongoing debate about the size of these corrections.

Abstract

We estimate the magnitude of the leading non-perturbative QCD corrections to the decays of the Higgs boson to the and final states. These corrections originate from the light-quark contributions to such decays. We show that the non-perturbative effects are suppressed by the small Yukawa couplings of light quarks, but that there is no further quark-mass suppression. This is at variance with what is found in the standard perturbative calculations of the light-quark contributions. We demonstrate that the non-perturbative corrections modify the and decay rates by , well below the expected precision with which such decays can be studied both at the high-luminosity LHC and at future colliders.

Paper Structure

This paper contains 5 sections, 33 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Higgs boson transition to two Z bosons
  3. Higgs boson decay to photon and Z boson
  4. Higgs boson decay to two photons
  5. Conclusions

Figures (2)

  • Figure 1: Contribution of light quarks to the $H \to Z^*Z^*$ transition: (a) an example of a short-distance perturbative diagram, (b) an example of the non-perturbative contribution. Terminated quark lines imply the quark condensate.
  • Figure 2: (a) The perturbative short-distance contribution to $H \to Z \gamma$. (b) The non-perturbative fragmentation of a $q \bar{q}$ pair to the photon distribution amplitude. Diagrams with the opposite fermion-flow direction are not shown.