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Heavy neutral leptons from kaon decays in the SHiP experiment
Physics Letters B ( IF 4.4 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.physletb.2020.135817
Dmitry Gorbunov , Igor Krasnov , Yury Kudenko , Sergey Suvorov

Abstract We calculate the signal rate of hypothetical heavy neutral leptons (HNL or sterile neutrinos) from kaon decays expected in the framework of the SHiP experiment. The kaons are produced in the hadronic shower initiated in the beam-dump mode by 400 GeV protons from CERN SPS. For a sufficiently light HNL (when the decays are kinematically allowed) we find kaon decays to be a noticeably richer source of HNL as compared to D-meson decays adopted in previous studies of the HNL phenomenology at SHiP. In particular, SHiP is capable of fully exploring the central part of the kinematically allowed region of the HNL mass and mixing with electron and muon neutrinos down to the lower cosmological bound. The latter is associated with HNL decays in the early Universe to energetic products rescattering off and thus destroying light nuclei produced at the primordial nucleosynthesis. A consistency of the HNL model with smaller mixing would require either a hierarchy – much larger mixing of all the HNL with tau neutrino – or non-standard cosmology and new ingredients in the HNL sector, closing the room for the minimal non-seesaw type I model with sterile neutrinos lighter than kaons.

中文翻译:

来自 kaon 的重中性轻子在 SHiP 实验中衰变

摘要 我们从 SHiP 实验框架中预期的 kaon 衰变计算假设的重中性轻子(HNL 或无菌中微子)的信号率。kaons 是在由来自 CERN SPS 的 400 GeV 质子以束流模式启动的强子簇射中产生的。对于足够轻的 HNL(当衰变在运动学上允许时),与 SHiP 先前对 HNL 现象学的研究中采用的 D-介子衰变相比,我们发现 kaon 衰变是一个明显更丰富的 HNL 来源。特别是,SHiP 能够充分探索 HNL 质量的运动学允许区域的中心部分,并与电子和 μ 中微子混合直至宇宙学下界。后者与早期宇宙中的 HNL 衰变有关,导致高能产物重新散射,从而破坏了原始核合成中产生的轻核。具有较小混合的 HNL 模型的一致性将需要层次结构——所有 HNL 与 tau 中微子的更大混合——或非标准宇宙学和 HNL 部门的新成分,为最小的非跷跷板类型 I 关闭空间具有比 kaons 轻的无菌中微子的模型。
更新日期:2020-11-01
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