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arXiv 2005.07102hep-phhep-ex
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介子衰变中暗粒子对的产生

Pair production of dark particles in meson decays

Matheus Hostert, Kunio Kaneta, Maxim Pospelov

备注：
25 pages, 9 figures, 1 table, v2: KOTO signal efficiency plots added. Accepted for publication in PRD
发表信息：
Phys. Rev. D 102, 055016 (2020)
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摘要：

$K$和$B$介子的罕见衰变提供了一个强有力的探测暗扇区与轻新粒子。我们发现，由于增强的二体运动学，$K_L\to X_1X_2$或$X_2X_2$，$O(100\,{\rm MeV})$暗态的对产生可以用$K_L$介子的衰变来探测。如果这两种粒子中有一种是不稳定的，例如$X_2\to X_1π^0$、$X_2\to X_1γ$或$X_{1,2}\to γγ$，这种衰变很容易模拟出$K_L\to π^0 ν\overlineν$的特征，同时不被带电K介子的衰变所排除。我们构建了明确的模型，增强了$K_L$衰变签名，并受到KOTO实验结果的约束。我们注意到，在满足所有其他约束（$B$衰变、对撞机、束流倾倒）的情况下，也可以容纳最近报告的多余事件。这些模型是基于规范和/或标量部门的理论的扩展。最轻的$X_{1,2}$粒子，如果稳定的话，可能构成整个暗物质。

英文摘要：

Rare decays of $K$ and $B$ mesons provide a powerful probe of dark sectors with light new particles. We show that the pair production of $O(100\,{\rm MeV})$ dark states can be probed with the decays of $K_L$ mesons, owing to the enhanced two-body kinematics, $K_L\to X_1X_2$ or $X_2X_2$. If either or these two particles is unstable, e.g. $X_2\to X_1π^0$, $X_2\to X_1γ$ or $X_{1,2}\to γγ$, such decays could easily mimic $K_L\to π^0 ν\overlineν$ signatures, while not being ruled out by the decays of charged kaons. We construct explicit models that have enhanced $K_L$ decay signatures, and are constrained by the results of the KOTO experiment. We note that recently reported excess events can also be accommodated while satisfying all other constraints ($B$ decays, colliders, beam dumps). These models are based on the extensions of the gauge and/or scalar sector of the theory. The lightest of $X_{1,2}$ particles, if stable, could constitute the entirety of dark matter.

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