AI 中文总结
研究未来 $e^+e^-$ 对撞机上由中性矢量玻色子 $Z_\ell$ 介导的亲轻子规范相互作用，聚焦 $e^+e^- \to \mu^+\mu^-$ 过程，利用角可观测量及干涉归一化量，考虑实际对撞机效应，得出不同对撞机配置下的预计灵敏度，展现了不同对撞机的互补性。
AI 中文摘要
我们对未来 $e^+e^-$ 对撞机中由中性矢量玻色子 $Z_\ell$ 介导的亲轻子规范相互作用进行了可观测量驱动的研究。聚焦于 $e^+e^- \to \mu^+\mu^-$ 过程，在干涉效应主导共振率增强的区域，研究角可观测量对离壳亲轻子相互作用的敏感性。分析以正反不对称性为中心，它能有力探测干涉引起的角变形且在共振区外仍保持敏感性。还引入干涉归一化量 $\mathcal{I}_{\rm FB}$ 作为诊断可观测量。考虑了包括初态辐射、束流辐射和有限能量分辨率等实际对撞机效应。利用FCC - ee、CEPC、ILC和CLIC的基准配置，在 $(M_{Z_\ell}, g_\ell)$ 平面得出预计灵敏度。结果表明高亮度圆形对撞机和高能线性对撞机之间具有互补性。总体而言，本框架为未来轻子对撞机通过干涉敏感角可观测量探测亲轻子规范相互作用提供了基于实验的方法。
英文摘要
We present an observable-driven study of leptophilic gauge interactions mediated by a neutral vector boson $Z_\ell$ at future $e^+e^-$ colliders. Focusing on the process $e^+e^- \to μ^+μ^-$, we investigate the sensitivity of angular observables to off-shell leptophilic interactions in regimes where interference effects dominate over resonant rate enhancements. The analysis is centered on the forward-backward asymmetry, which provides a robust probe of interference-induced angular deformations and retains sensitivity well beyond the resonance region. To characterize the relative angular response independently of the overall rate modification, we additionally introduce the interference-normalized quantity $\mathcal{I}_{\rm FB}$ as a diagnostic observable. Realistic collider effects, including initial-state radiation, beamstrahlung, and finite energy resolution, are consistently incorporated. Using benchmark configurations for FCC-ee, CEPC, ILC, and CLIC, we derive projected sensitivities in the $(M_{Z_\ell}, g_\ell)$ plane. The results demonstrate the complementarity between high-luminosity circular colliders and high-energy linear colliders, reflecting the interplay between precision measurements and the energy enhancement of interference effects. Overall, the present framework provides an experimentally grounded approach for probing leptophilic gauge interactions through interference-sensitive angular observables at future lepton colliders.
Comments28 pages, 8 figures, published in Physical Review D (2026). Minor correction to the reference list
Journal refPhysical Review D 114 (2026) 015009
