AI 中文总结
该研究计算类矢量费米子对FCC-ee希格斯辐射产生截面的单圈效应，发现汤川驱动情景的参数空间可产生达FCC-ee灵敏度的偏移，为相关耦合提供辐射探针，指出类矢量汤川耦合是更优测量目标。
AI 中文摘要
我们计算类矢量费米子（VLFs）对希格斯辐射产生截面的单圈效应，希格斯辐射产生截面是未来如FCC-ee这类e⁺e⁻希格斯工厂的旗舰精密可观测量。我们考虑标准模型（SM）的四个基准扩展情景：两个情景中，一个类矢量夸克（VLQ）或类矢量轻子（VLL）二重态与其单态伙伴通过纯内部汤川相互作用耦合到希格斯玻色子；另外两个情景中，单个类矢量单态直接与第三代带电轻子或中微子混合。我们全程采用在壳重整化方案，并在重整化群（RG）跑动下对相关耦合施加微扰性约束，计算了单圈阶希格斯辐射产生振幅的通用自能贡献与非通用顶点贡献，同时还计算了斜参数S、T以及H→γγ衰变率作为互补交叉检验。在两个汤川驱动的情景中，我们发现当前LHC搜索仍允许的相当一部分参数空间会使σ(ZH)产生千分之一或更高水平的偏移，达到FCC-ee预期的灵敏度，为这些耦合提供了辐射探针。在两个混合驱动的情景中，现有的对相关混合角的电弱精密约束已排除了可观测效应，不过我们为未来参考全面表征了潜在的圈动力学。这些结果表明，类矢量汤川耦合而非其与SM费米子的任何残余混合，是未来e⁺e⁻对撞机希格斯辐射产生精密测量更具前景的目标。
英文摘要
We compute the one-loop effects of vector-like fermions (VLFs) on the Higgs-strahlung cross-section, the flagship precision observable of future $e^+e^-$ Higgs factories such as FCC-ee. We consider four benchmark extensions of the Standard Model (SM): two in which a VL quark (VLQ) or VL lepton (VLL) doublet, together with its singlet partners, couples to the Higgs boson through purely internal Yukawa interactions, and two in which a single VL singlet mixes directly with the third-generation charged lepton or neutrino. Working throughout in the on-shell renormalization scheme and imposing perturbativity bounds on the relevant couplings under renormalization-group (RG) running, we compute both the universal self-energy and the non-universal vertex contributions to the Higgs-strahlung amplitude at one loop, together with the oblique parameters $S$ and $T$ and the $H\toγγ$ rate as complementary cross-checks. In the two Yukawa-driven scenarios, we find that a sizable fraction of the parameter space still allowed by current LHC searches produces shifts in $σ(ZH)$ at or above the per-mille sensitivity envisioned for FCC-ee, offering a radiative probe of these couplings. In the two mixing-driven scenarios, existing electroweak-precision bounds on the relevant mixing angles already preclude an observable effect, although we characterize the underlying loop dynamics in full generality for future reference. These results identify the VL Yukawa couplings, rather than any residual mixing with the SM fermions, as the more promising target for Higgs-strahlung precision measurements at a future $e^+e^-$ collider.
Comments46 pages, 17 figures, 4 tables, 4 ancillary files
