U(3)手征理论框架下K介子衰变产生的类轴子粒子
Axion-like particle production from kaon decays within U(3) chiral theory
AI总结：
本研究在U(3)手征微扰论领头阶计算K介子衰变产生类轴子粒子的振幅，纳入末态相互作用并拟合实验数据确定弱低能常数，结合多个实验结果推导对类轴子粒子耦合的约束。
AI中文摘要：
K介子衰变尤其是通过$K\toπa$过程，为类轴子粒子（ALP）提供了重要的约束条件。本研究在U(3)手征微扰理论的领头阶计算了$K\toπa$衰变振幅以及$K\toππ$衰变振幅，并采用手征幺正化方法纳入了两个过程中的$ππ$末态相互作用效应。相关的弱低能常数通过拟合$K\toππ$衰变的实验数据确定。数值分析表明，$η_0$对$K\toπa$振幅的显式贡献很小，而U(3)理论特有的新弱算符可产生相当大的贡献。研究发现，$ππ$末态相互作用在$K^\pm\toπ^\pm a$衰变中影响不显著，但在$K^0/\bar{K}^0\toπ^0a$道中作用明显。我们根据NA62最新的$K^+\toπ^+ +不可见$衰变上限推导了对ALP耦合的约束。为完整起见，我们还纳入了来自KOTO对$K_L\toπ^0+不可见$的搜寻、NA62对$K^+\toπ^+γγ$的测量以及NA48对$K_S\toπ^0γγ$的测量所得的约束。
英文摘要：
Kaon decays provide important constraints on the axion-like particle (ALP), particularly through the $K\toπa$ processes. In this work, we compute the $K\toπa$ decay amplitudes, as well as the $K\toππ$ decay amplitudes, at leading order within U(3) chiral perturbation theory. The $ππ$ final-state interaction effects in both processes are implemented by employing the chiral unitarization approach. The relevant weak low-energy constants are determined by fitting to the experimental data on $K\toππ$ decays. Our numerical analysis shows that the explicit $η_0$ contribution to the $K\toπa$ amplitudes is small, whereas the new weak operator unique to the U(3) theory can give a sizable contribution. The $ππ$ final-state interactions are found to be insignificant in the $K^\pm\toπ^\pm a$ decays, but give pronounced effects in the $K^0/\bar{K}^0\toπ^0a$ channels. Constraints on the ALP couplings are derived from the most recent NA62 upper limit on the $K^+\toπ^+ +invisible$ decay. For completeness, we also include constraints from the KOTO search for $K_L\toπ^0+ invisible$, the NA62 measurement of $K^+\toπ^+γγ$, and the NA48 measurement of $K_S\toπ^0γγ$.
