We present a proof-of-concept extension to the Standard Model that can generate a non-vanishing neutrinoless double beta decay (0νββ) signal without the existence of Majorana neutrinos or lepton number violation in the zero-density vacuum-ground-state Lagrangian. We propose that the 0νββ can be induced by the capture of an ultralight scalar field, a potential dark matter candidate, that carries two units of lepton number. This makes the observable 0νββ spectrum indistinguishable from the usual 0νββ mechanisms by any practical means. We find that a non-zero 0νββ rate does not require neutrinos to be fundamentally Majorana particles. However, for sizeable decay rates within the range of next-generation experiments, the neutrino will, generally, acquire an (effective) Majorana mass as the scalar field undergoes a transition to the Bose-Einstein condensate phase. We also discuss the distinction between the aforementioned scenario and the case in which the emission of a lepton-number-two scalar leads to 0νββ, exhibiting discernible qualitative features that make it experimentally distinguishable from the conventional scenario.

中文翻译：

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无真空的无中微子双 β 衰变 Majorana 中微子质量


我们提出了标准模型的概念验证扩展，它可以产生不消失的无中微子双 β 衰变 （0νββ） 信号，而在零密度真空基态拉格朗日中不存在马约拉纳中微子或轻子数违规。我们提出 0νββ 可以通过捕获超轻标量场来诱导，超轻标量场是一种潜在的暗物质候选者，带有两个轻子数单位。这使得可观测的 0νββ 光谱无法通过任何实际方式与通常的 0νββ 机制区分开来。我们发现非零 0νββ 速率不需要中微子从根本上是马约拉纳粒子。然而，对于下一代实验范围内的相当大的衰变率，当标量场经历向玻色-爱因斯坦凝聚态相的转变时，中微子通常会获得（有效的）马约拉纳质量。我们还讨论了上述情景与轻子数 2 标量发射导致 0νββ 的情况之间的区别，表现出可辨别的定性特征，使其在实验上与传统情景区分开来。