Next-to-Next-to-Leading Order QCD Corrections to ηt → HZ
Abstract
Motivated by recent LHC observations of a threshold enhancement in the tt̅ system consistent with toponium-like dynamics, we compute the next-to-next-to-leading order (NNLO) QCD correction to the hard short-distance coefficient for ηt→ HZ, where ηt denotes the pseudoscalar color-singlet configuration tt̅(1S0[1]). Within the NRQCD factorization framework, we retain the full dependence on the Higgs- and Z-boson masses and include both the two-loop virtual corrections and the real double-gluon-emission channel. At next-to-leading order (NLO), the finite-mass result remains close to its large-mass limit. The NNLO coefficient develops logarithms of both the renormalization scale μR and the NRQCD factorization scale μΛ. For μR=μΛ=mt, the NLO and NNLO terms suppress the leading-order width by about 29% and 19%, respectively; the two-loop contribution is about two thirds of the one-loop effect and of the same sign, so the perturbative series converges slowly and the NNLO prediction amounts to about 52% of the leading-order width. The resulting coefficient provides a necessary ingredient for future threshold studies of ηt→ HZ and for assessing the sensitivity of this channel to the top-Higgs interaction. The accuracy of the result is further supported by three checks: reproduction of the known large-mass limit at one loop, independence of the extracted coefficient on the γ5 prescription, and consistency of its scale logarithms with the renormalization-group structure.
Related
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- Next-to-leading order QCD corrections to fully charm tetraquark radiative decays
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BibTeX
@misc{jia2026nexttonexttoleading,
title = {{Next-to-Next-to-Leading Order QCD Corrections to $η_t \to HZ$}},
author = {Cai-Ping Jia and Yan-Qing Ma and Huai-Min Yu and Yu-Jie Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34364},
eprint = {2609.34364},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34364},
}
RIS
TY - UNPB
TI - Next-to-Next-to-Leading Order QCD Corrections to η_t → HZ
AU - Cai-Ping Jia
AU - Yan-Qing Ma
AU - Huai-Min Yu
AU - Yu-Jie Zhang
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34364
UR - https://arxiv.org/abs/2609.34364
AB - Motivated by recent LHC observations of a threshold enhancement in the tt̅ system consistent with toponium-like dynamics, we compute the next-to-next-to-leading order (NNLO) QCD correction to the hard short-distance coefficient for η_t→ HZ, where η_t denotes the pseudoscalar color-singlet configuration tt̅(^1S_0^[1]). Within the NRQCD factorization framework, we retain the full dependence on the Higgs- and Z-boson masses and include both the two-loop virtual corrections and the real double-gluon-emission channel. At next-to-leading order (NLO), the finite-mass result remains close to its large-mass limit. The NNLO coefficient develops logarithms of both the renormalization scale μ_R and the NRQCD factorization scale μ_Λ. For μ_R=μ_Λ=m_t, the NLO and NNLO terms suppress the leading-order width by about 29% and 19%, respectively; the two-loop contribution is about two thirds of the one-loop effect and of the same sign, so the perturbative series converges slowly and the NNLO prediction amounts to about 52% of the leading-order width. The resulting coefficient provides a necessary ingredient for future threshold studies of η_t→ HZ and for assessing the sensitivity of this channel to the top-Higgs interaction. The accuracy of the result is further supported by three checks: reproduction of the known large-mass limit at one loop, independence of the extracted coefficient on the γ_5 prescription, and consistency of its scale logarithms with the renormalization-group structure.
ER -