发表机构
INFN, Sezione di Trieste; University of Trieste; NICPB; INFN, Laboratori Nazionali di Frascati（意大利国家核物理研究所的里雅斯特分部; 的里雅斯特大学; 国家化学物理与生物物理研究所; 意大利国家核物理研究所弗拉斯卡蒂国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究提出通过带电 kaon 衰变中的双π子和辐射通道搜索暗光子，利用手征夸克模型计算灵敏度，为 NA62 及未来设施提供探测目标。
AI 中文摘要
我们研究了通过双π子道 $K^+\to\pi^+\pi^0\\,\gamma_D$ 和单π子辐射衰变 $K^+\to\pi^+\gamma\\,\gamma_D$ 在带电 kaon 衰变中探测不可见暗光子的前景，其中 $\gamma$ 和 $\gamma_D$ 分别表示普通光子和暗光子。前一种衰变先前被提议作为 NA62 上无质量暗光子搜索的黄金通道，而在这里我们引入辐射过程作为互补探针，并将两种分析扩展到有质量暗光子。三体模式在低暗光子质量下尤为重要，此时两体衰变 $K^+\to\pi^+\\,\gamma_D$ 被强烈抑制，并在无质量极限下消失。对于无质量暗光子，由动力学混合诱导的可重整化相互作用不存在，主导贡献来自由维度五磁偶极算符介导的有效非重整化味改变夸克相互作用 $s\to d\\,\gamma_D$。对于有质量暗光子也是如此。在考虑现有的混合参数约束后，它们的动力学混合对这些通道的贡献可忽略不计。只有与无质量情况相同的味改变磁偶极算符是相关的。使用手征夸克模型，我们估计了偶极算符的相关强子矩阵元，并考虑了来自 $K^+\to\pi^+\\,X$（其中 $X$ 表示共振缺失能量）、$K^+\to\pi^+\nu\bar\nu$ 和 $K^0\\!\\!-\\!\bar{K}^0$ 混合的约束。基于这些计算，我们确定了这些衰变模式的允许分支比以及 NA62 和未来带电 kaon 设施所需的灵敏度。
英文摘要
We investigate the prospects for detecting invisible dark photons in charged kaon decays through the two-pion channel $K^+\toπ^+π^0\,γ_D$ and the one-pion radiative decay $K^+\toπ^+γ\,γ_D$, where $γ$ and $γ_D$ denote the ordinary photon and dark photon, respectively. The former decay was previously proposed as a golden channel for massless dark photon searches at NA62, while here we introduce the radiative process as a complementary probe and extend both analyses to massive dark photons. The three-body modes are particularly relevant at low dark photon masses, where the two-body decay $K^+\toπ^+\, γ_D$ becomes strongly suppressed and vanishes in the massless limit. For massless dark photons, renormalizable interactions induced by kinetic mixing are absent, and the dominant contribution arises from the effective non-renormalizable flavor-changing quark interaction $s\to d\, γ_D$ mediated by a dimension-five magnetic-dipole operator. This is also true for massive dark photons. Their kinetic mixing contributes negligibly to these channels, after considering the existing bounds on the mixing parameter. Only the same flavor changing magnetic-dipole operator as in the massless case is relevant. Using the chiral quark model, we estimate the relevant hadronic matrix elements of the dipole operator and account for constraints from $K^+\toπ^+\,X$, where $X$ denotes resonant missing energy, $K^+\toπ^+ν\barν$, and $K^0\!\!-\!\bar{K}^0$ mixing. Based on these calculations, we determine the allowed branching ratios for these decay modes and the sensitivities required at NA62 and future charged-kaon facilities.
Comments19 pages, 6 figures
