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arXiv 2402.07993hep-phnucl-th
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轻惰性中微子存在下的无中微子双β衰变率

Neutrinoless double beta decay rates in the presence of light sterile neutrinos

W. Dekens, J. de Vries, D. Castillo, J. Menéndez, E. Mereghetti, V. Plakkot, P. Soriano, G. Zhou

AI总结:

本文研究含右手中微子的标准模型最小扩展中的 $0νββ$,指出超软动量交换和短程项的重要贡献,并给出 ${}^{76}$Ge、${}^{136}$Xe 核矩阵元及 $3+2$ 模型分析。

摘要:

我们在粒子物理标准模型的最小扩展中研究无中微子双β衰变($0νββ$),在这些扩展中,规范单态右手中微子产生 Dirac 质量项和 Majorana 中微子质量项。我们认为,对这些情形基于质量依赖的核矩阵元的标准处理,遗漏了对 $0νββ$ 振幅的重要贡献。首先,新效应来自具有极小(超软)动量的中微子交换,我们为此计算了 ${}^{76}$Ge 和 ${}^{136}$Xe 衰变的相关核矩阵元。在存在轻惰性中微子的情况下,这些贡献可能主导 $0νββ$ 衰变率。超软项在仅有三个轻 Majorana 中微子这一更标准的情形中也具有相关性,会使总 $0νββ$ 振幅降低 $10\%$。其次,我们强调了与中等质量惰性中微子相关的短程项的重要性,并提供了可用于唯象分析的显式公式。作为示例,我们讨论了这些新效应在若干显式情形中的影响,包括具有两个右手规范单态中微子的现实 $3+2$ 模型。

英文摘要:

We investigate neutrinoless double-beta decay ($0νββ$) in minimal extensions of the Standard Model of particle physics where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We argue that the standard treatment of these scenarios, based on mass-dependent nuclear matrix elements, is missing important contributions to the $0νββ$ amplitude. First, new effects arise from the exchange of neutrinos with very small (ultrasoft) momenta, for which we compute the associated nuclear matrix elements for the decays of ${}^{76}$Ge and ${}^{136}$Xe. These contributions can dominate the $0νββ$ rate in cases with light sterile neutrinos. The ultrasoft terms are also relevant in the more standard scenario of just three light Majorana neutrinos where they lead to a $10\%$ reduction of the total $0νββ$ amplitude. Secondly, we highlight the importance of short-range terms associated with medium-heavy sterile neutrinos and provide explicit formulae that can be used in phenomenological analyses. As examples we discuss impact of these new effects in several explicit scenarios, including a realistic $3+2$ model with two right-handed gauge-singlet neutrinos.

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