在FCC-ee上从β衰变的新物理中解缠$V_{ud}$
Disentangling $V_{ud}$ from New Physics in Beta Decays with the FCC-ee
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中文总结 AI 辅助
本研究结合低能β衰变数据与未来对撞机预期，在SMEFiT框架内同时确定$V_{ud}$和SMEFT Wilson系数，证明FCC-ee能完全解耦$V_{ud}$与新物理，恢复标准模型精度并加强约束，为CKM幺正性检验提供一致解释。
中文摘要 AI 辅助
超允许核β衰变能够最精确地确定CKM矩阵元$V_{ud}$，但它们仅对$V_{ud}$与左手带电电流中新物理贡献的有效组合敏感，仅靠低能数据无法区分这两者。在此，我们在SMEFiT框架内，通过将针对超允许跃迁的专用似然函数（包括辐射和核结构不确定性）与LEP和LHC的全球数据以及HL-LHC和FCC-ee的预期数据相结合，同时确定$V_{ud}$和标准模型有效场论（SMEFT）中相关的Wilson系数。当前的对撞机数据和HL-LHC预期只能部分解除$V_{ud}$与可能的新物理效应之间的简并。相反，FCC-ee能完全将$V_{ud}$与新物理解耦，恢复SM级别的精度，同时显著加强对SMEFT Wilson系数的约束。这一结论对味假设和理论不确定性的变化具有稳健性。我们的结果凸显了未来对撞机与低能实验之间的互补性，并为第一行CKM幺正性检验和Cabibbo角异常提供SMEFT一致解释铺平了道路。
英文摘要
Superallowed nuclear $β$-decays enable the most precise determination of the CKM element $V_{ud}$, but they are only sensitive to an effective combination of $V_{ud}$ and New Physics contributions to left-handed charged currents, which low-energy data alone cannot disentangle. Here we determine $V_{ud}$ simultaneously with the relevant Wilson coefficients of the Standard Model Effective Field Theory (SMEFT) by combining, within the SMEFiT framework, a dedicated likelihood for superallowed transitions, including radiative and nuclear-structure uncertainties, with LEP and LHC world data and HL-LHC and FCC-ee projections. Current collider data and HL-LHC projections only partially lift the degeneracy between $V_{ud}$ and possible New Physics effects. Instead, the FCC-ee fully decouples $V_{ud}$ from New Physics, recovering SM-level precision while significantly tightening the constraints on the SMEFT Wilson coefficients. This conclusion is robust against variations in flavour assumptions and theory uncertainties. Our results highlight the complementarity between future colliders and low-energy experiments, and pave the way towards a SMEFT-consistent interpretation of first-row CKM unitarity tests and the Cabibbo angle anomaly.
发表机构
- Nikhef Theory Group（NIKHEF理论组）
- Institute of Physics, Universiteit van Amsterdam（阿姆斯特丹大学物理研究所）
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam（阿姆斯特丹自由大学物理与天文学系）
- Institute for Nuclear Theory, University of Washington（华盛顿大学核理论研究所）
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