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arXiv 2402.05901hep-phhep-ex
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解释 $B^+\to K^+ ν\barν$ 超出：通过无质量暗光子

Explaining the $B^+\to K^+ ν\barν$ excess via a massless dark photon

E. Gabrielli, L. Marzola, K. Müürsepp, M. Raidal

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17 pages, 3 figures
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AI总结：

本文提出无质量暗光子通过色磁偶极耦合解释 Belle II 观测到的 $B^+\to K^+ ν\barν$ 超出，并预言 $B^0\to K^* γ_D$ 和 $B^0_s\to ϕ+E_{\rm miss}$ 中的新信号。

摘要：

Belle II 合作组最近观测到了稀有衰变 $B^+\to K^+ ν\barν$，发现其相对于标准模型预言存在超出。我们探讨了该数据可能源于由无质量暗光子 $γ_{\scriptscriptstyle{D}}$ 诱导的长程相互作用的可能性。该暗光子在树级上与不可见的暗扇区耦合，并通过高维算符（如我们用来解释该超出的色磁偶极耦合）与标准模型耦合。由于 $B^+\to K^+ γ_{\scriptscriptstyle{D}}$ 过程被角动量守恒所禁止，由离壳暗光子介导的跃迁产生一个三体末态，包含一对暗费米子，它们在探测器中表现为缺失能量连续谱，从而模拟中微子信号。我们表明，对于模型的微扰参数值，Belle II 数据可以得到解释。该场景预言了中性 $B$ 介子衰变 $B^0\to K^* γ_{\scriptscriptstyle{D}}$ 的新贡献，其中允许发射在壳暗光子，产生单色缺失能量信号。类似地，对于 $B^0_s\to ϕ+ E_{\rm miss}$ 衰变，预言了由暗光子发射导致的超出，该衰变可在接下来的 LHCb 实验中得到仔细检验。

英文摘要：

The Belle II collaboration has recently observed the rare decay $B^+\to K^+ ν\barν$, finding an excess with respect to the Standard Model prediction. We explore the possibility that the data entails long-distance interactions induced by a massless dark photon, $γ_{\scriptscriptstyle{D}}$. This couples at the tree-level to an invisible, dark sector and to the Standard Model via higher-dimensional operators, such as the chromomagnetic-dipole coupling that we use to explain the excess. As the process $B^+\to K^+ γ_{\scriptscriptstyle{D}}$ is forbidden by angular momentum conservation, the transition mediated by the off-shell dark photon yields a three-body final state comprising a pair of dark fermions that show as a missing energy continuum in the detector, faking the neutrino signature. We show that the Belle II data is explained for perturbative values of the parameters of the model. This scenario predicts new contributions to the neutral $B$ meson decays $B^0\to K^* γ_{\scriptscriptstyle{D}}$, in which the emission of a on-shell dark photon is allowed, yielding a monochromatic missing energy signature. Analogously, an excess due to the emission of a dark photon is predicted for the $B^0_s\to ϕ+ E_{\rm miss}$ decay that could be scrutinized next at the LHCb experiments.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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