Higgs pseudo-observables in e^+e^-→ hγ

Abstract

We analyse the process e⁺e^-→ hγ in the Standard Model (SM) and in generic extensions with heavy new physics, using the framework of Higgs pseudo-observables. We decompose the one-loop amplitude into separately gauge-invariant photon-pole, Z-pole, and non-pole contributions. For heavy new physics, we show that the leading deviations from the SM are necessarily encoded in the hγγ and hZγ on-shell effective couplings. Genuine e⁺e^-hγ contact interactions arise only at higher orders in a derivative expansion, both in SMEFT and HEFT. Although Higgs decays constrain the magnitudes of these pseudo-observables, they leave their relative sign undetermined. Measurements of e⁺e^-→ hγ at different FCC-ee energies can resolve this ambiguity. Deviations incompatible with this description would instead point towards relatively light new degrees of freedom, as illustrated by a simplified Z' model.

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BibTeX RIS

BibTeX

@misc{boniotti2026higgs,
  title = {{Higgs pseudo-observables in $e^+e^-\to hγ$}},
  author = {Fausto Boniotti and Gino Isidori and Christiane Mayer and Emanuelle Pinsard},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.35981},
  eprint = {2609.35981},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.35981},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Higgs pseudo-observables in e^+e^-→ hγ
AU  - Fausto Boniotti
AU  - Gino Isidori
AU  - Christiane Mayer
AU  - Emanuelle Pinsard
PY  - 2026
DA  - 2026/09/28
PB  - arXiv
DO  - 10.48550/arxiv.2609.35981
UR  - https://arxiv.org/abs/2609.35981
AB  - We analyse the process e^+e^-→ hγ in the Standard Model (SM) and in generic extensions with heavy new physics, using the framework of Higgs pseudo-observables. We decompose the one-loop amplitude into separately gauge-invariant photon-pole, Z-pole, and non-pole contributions. For heavy new physics, we show that the leading deviations from the SM are necessarily encoded in the hγγ and hZγ on-shell effective couplings. Genuine e^+e^-hγ contact interactions arise only at higher orders in a derivative expansion, both in SMEFT and HEFT. Although Higgs decays constrain the magnitudes of these pseudo-observables, they leave their relative sign undetermined. Measurements of e^+e^-→ hγ at different FCC-ee energies can resolve this ambiguity. Deviations incompatible with this description would instead point towards relatively light new degrees of freedom, as illustrated by a simplified Z' model.
ER  -

Higgs pseudo-observables in e⁺e^-→ hγ

Abstract

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