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Higgs CAT

Giampiero Passarino

TL;DR

This work argues that precision Higgs physics cannot rely solely on on-shell, narrow-width approximations. It develops a complex-pole, pseudo-observable framework to treat off-shell Higgs production and decay, explicitly accounting for signal-background interference and higher-order uncertainties. By comparing zero, soft, and intermediate K-factor schemes and proposing LO MC reweighting and THU-based morphing approaches, the paper provides practical strategies to quantify and reduce theoretical uncertainties in off-shell regions. The findings emphasize that THU, particularly from interference, dominates the error budget and that off-shell measurements offer a path to constraining the Higgs width and couplings in a largely model-independent way, contingent on robust MC-based analyses.

Abstract

Higgs Computed Axial Tomography, an excerpt. Taking a closer look at the camel-shaped tail of the light Higgs boson resonance and looking to the transformation of the (camel-shaped) signal into a square-root--shaped signal + interference with particular emphasis on residual theoretical uncertainties.

Higgs CAT

TL;DR

This work argues that precision Higgs physics cannot rely solely on on-shell, narrow-width approximations. It develops a complex-pole, pseudo-observable framework to treat off-shell Higgs production and decay, explicitly accounting for signal-background interference and higher-order uncertainties. By comparing zero, soft, and intermediate K-factor schemes and proposing LO MC reweighting and THU-based morphing approaches, the paper provides practical strategies to quantify and reduce theoretical uncertainties in off-shell regions. The findings emphasize that THU, particularly from interference, dominates the error budget and that off-shell measurements offer a path to constraining the Higgs width and couplings in a largely model-independent way, contingent on robust MC-based analyses.

Abstract

Higgs Computed Axial Tomography, an excerpt. Taking a closer look at the camel-shaped tail of the light Higgs boson resonance and looking to the transformation of the (camel-shaped) signal into a square-root--shaped signal + interference with particular emphasis on residual theoretical uncertainties.

Paper Structure

This paper contains 16 sections, 1 theorem, 34 equations, 11 figures, 2 tables.

Table of Contents

  1. Introduction
  2. An old idea
  3. Higgs intrinsic width
  4. The wrath of the "heavy" Higgs
  5. Higgs boson Production and decay: the analytic structure
  6. More on production cross-section
  7. An idea that is not dangerous is unworthy of being called an idea at all
  8. When the going gets tough, interference gets going
  9. The zero-knowledge scenario
  10. There is no free lunch
  11. How to use an LO MC?
  12. Improving THU for Interference?
  13. The soft-knowledge scenario
  14. Background-subtracted lineshape
  15. Conclusions
  16. ...and 1 more sections

Key Result

Proposition 3.1

The familiar concept of on-shell production$\,\otimes\,$branching ratio can be generalized to It is also convenient to rewrite the result as where we have introduced a sum over all final states,

Figures (11)

  • Figure 1: The NNLO ${} { {} { { {{\bm{ { {\mathsf{ {} {} {{V}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{V}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace$ invariant mass distribution in ${} { {} { { {{\bm{ { {\mathsf{ {} {} {{g}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{g}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace \to {} { {} { { {{\bm{ { {\mathsf{ {} {} {{V}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{V}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace$ for $\mu{ {} { {} { { {{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace}$μ_ ${{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}}$$= 125~\text{GeV}$.
  • Figure 2: The LO ${} { {} { { {{\bm{ { {\mathsf{ {} {} {{Z}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{Z}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace$ invariant mass distribution ${} { {} { { {{\bm{ { {\mathsf{ {} {} {{g}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{g}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace \to {} { {} { { {{\bm{ { {\mathsf{ {} {} {{Z}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{Z}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace$ for $\mu{ {} { {} { { {{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace}$μ_ ${{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}}$$= 125~\text{GeV}$. The black line is the total, the red line gives the signal while the cyan line gives signal plus background; the blue line includes the $q\bar{q} \to {} { {} { { {{\bm{ { {\mathsf{ {} {} {{Z}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace {} { {} { { {{\bm{ { {\mathsf{ {} {} {{Z}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace$ contribution.
  • Figure 3: Differential $K\,$-factors in Higgs production for $\mu{ {} { {} { { {{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace}$μ_ ${{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}}$$= 125.6~\text{GeV}$.
  • Figure 4: Electroweak theoretical uncertainty for the signal lineshape at $\mu{ {} { {} { { {{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace}$μ_ ${{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}}$$= 125.6~\text{GeV}$
  • Figure 5: Ratio of Breit-Wigner and Complex Pole distributed cross sections at $\mu{ {} { {} { { {{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}} } } } \xspace}$μ_ ${{\bm{ { {\mathsf{ {} {} {{H}_{ {\!\mspace{1mu}} }^{}} \mspace{-0.6mu} }} } }}}$$= 125.6~\text{GeV}$
  • ...and 6 more figures

Theorems & Definitions (1)

  • Proposition 3.1