发表机构
Northwest Normal University; Peking University; INFN, Sezione di Milano-Bicocca; Beihang University（西北师范大学; 北京大学; 意大利国家核物理研究所米兰-比可卡分部; 北京航空航天大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
计算 $\eta_t\to HZ$ 的 NNLO QCD 修正，保留质量依赖，发现微扰级数收敛缓慢，NNLO 预言约为领头阶宽度的 52%，为阈值研究和顶-希格斯相互作用灵敏度提供关键输入。
AI 中文摘要
受近期大型强子对撞机（LHC）在 $t\bar t$ 系统中观测到与类 toponium 动力学一致的阈值增强现象的启发，我们计算了 $\eta_t\to HZ$ 的硬短距离系数的次次领头阶（NNLO）QCD 修正，其中 $\eta_t$ 表示赝标量色单态组态 $t\bar t({}^1S_0^{[1]})$。在非相对论 QCD（NRQCD）因子化框架内，我们保留了希格斯玻色子与 $Z$ 玻色子质量的完整依赖，并同时包含了双圈虚修正和实双胶子发射道。在次领头阶（NLO）下，有限质量结果与其大质量极限保持接近。NNLO 系数产生重整化尺度 $\mu_R$ 与 NRQCD 因子化尺度 $\mu_\Lambda$ 的对数。对于 $\mu_R=\mu_\Lambda=m_t$，NLO 和 NNLO 项分别压低领头阶宽度约 $29\\%$ 和 $19\\%$；双圈贡献约为单圈效应的三分之二且符号相同，因此微扰级数收敛缓慢，NNLO 预言约为领头阶宽度的 $52\\%$。所得系数为未来 $\eta_t\to HZ$ 的阈值研究以及评估该道对顶-希格斯相互作用的灵敏度提供了必要要素。结果的准确性进一步由三项检验支持：在单圈水平复现已知的大质量极限、提取的系数对 $\gamma_5$ 方案的独立性，以及其尺度对数与重整化群结构的一致性。
英文摘要
Motivated by recent LHC observations of a threshold enhancement in the $t\bar t$ 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 $η_t\to HZ$, where $η_t$ denotes the pseudoscalar color-singlet configuration $t\bar t({}^1S_0^{[1]})$. 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 $η_t\to HZ$ 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.
Comments8 pages,3 figures
