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arXiv 2005.09575hep-ex
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在$K^+$衰变为正电子过程中寻找重中性轻子的产生

Search for heavy neutral lepton production in $K^+$ decays to positrons

NA62 collaboration

摘要:

利用2017- 2018年欧洲核子研究中心(CERN)NA 62实验收集的数据样本,研究了重中性轻子($N$)在$K^+\to e^+N$衰变中的产生.扩展中微子混合矩阵元$|U_{e4}|^2$的上限是在$10^{-9}$水平上建立的,在大部分可达的重中性轻子质量范围144- 462 MeV/ $c^2$,假设寿命超过50 ns。这些限制大大提高了以前的生产和衰变搜索。大爆炸核合成所支持的$|U_{e4}|^2$范围被排除在大约340 MeV/ $c^2$的质量之外。

英文摘要:

A search for heavy neutral lepton ($N$) production in $K^+\to e^+N$ decays using the data sample collected by the NA62 experiment at CERN in 2017--2018 is reported. Upper limits of the extended neutrino mixing matrix element $|U_{e4}|^2$ are established at the level of $10^{-9}$ over most of the accessible heavy neutral lepton mass range 144--462 MeV/$c^2$, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The $|U_{e4}|^2$ range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/$c^2$.

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