发表机构
Deutsches Elektronen-Synchrotron DESY; Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering; INFN, Laboratori Nazionali di Frascati; Institut für Physik, Humboldt-Universität zu Berlin（德国电子同步加速器; 霍里亚·胡卢贝伊核物理与核工程研发国家研究所; 意大利国家核物理研究院弗拉斯卡蒂国家实验室; 柏林洪堡大学物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究探讨纯轻子带电流K、π介子衰变精密测量的前景，关注可抵消实验不确定度的单比率及探测新物理的双比率，结合实验与理论进展，评估其对超出标准模型物理搜索的约束作用。
AI 中文摘要
我们研究纯轻子带电流K介子和π介子衰变的精密测量的未来前景，尤其关注单比率$R_{K\pi}^{\ell=\mu,e} = \Gamma(K \to \ell\nu) / \Gamma(\pi \to \ell\nu)$（该比率可抵消大量实验不确定度），以及双比率$R_{K\pi}^e / R_{K\pi}^\mu$（对新物理具有极强探测灵敏度）。该研究恰逢两大进展交汇的契机：实验方面，基于慢引出质子束的专用装置的新概念设计及多年数据采集计划，有望达到$10^{-4}$量级的测量精度；理论方面，近期格点量子色动力学（lattice-QCD）计算已达到相当的精度水平。最后，我们评估这些下一代测量对超出标准模型的物理搜索的影响，结果显示它们能提供与现有限制具有竞争力或互补性的约束条件。
英文摘要
We study the future prospects for precision measurements of purely leptonic charged-current kaon and pion decays. Together with the ratio of leptonic widths $R_K^ν=Γ(K\to eν)/Γ(K\toμν)$, we consider the single ratios $R_{Kπ}^{\ell=μ,e} = Γ(K \to \ellν) / Γ(π\to \ellν)$, for which many experimental uncertainties cancel, as well as the double ratio $R_{Kπ}^e / R_{Kπ}^μ$, which provides a particularly sensitive probe of new physics. This study is timely in light of two converging developments. On the experimental side, a new conceptual design for a dedicated setup based on a slow-extracted proton beam and a multi-year data-taking program, is expected to achieve a precision at the few $10^{-4}$ level. On the theory side, recent lattice-QCD calculations have reached a comparable level of accuracy. Finally, we assess the impact of these next-generation measurements on searches for physics beyond the Standard Model and show that they can provide constraints that are either competitive with or complementary to existing bounds.
Comments43 pages, 17 figures. Version submitted to JHEP
