Toward the discovery of matter creation with neutrinoless ββ decay

Abstract

The discovery of neutrinoless ββ decay could soon be within reach. This hypothetical ultrarare nuclear decay offers a privileged portal to physics beyond the standard model of particle physics. Its observation would constitute the discovery of a matter-creating process, corroborating leading theories of why the Universe contains more matter than antimatter, and how forces unify at high energy scales. It would also prove that neutrinos and antineutrinos are not two distinct particles but can transform into each other, with their mass described by a unique mechanism conceived by Majorana. The recognition that neutrinos are not massless necessitates an explanation and has boosted interest in neutrinoless ββ decay. The field stands now at a turning point. A new round of experiments is currently being prepared for the next decade to cover an important region of parameter space. In parallel, advances in nuclear theory are laying the groundwork to connect the nuclear decay with the underlying new physics. Meanwhile, the particle theory landscape continues to find new motivations for neutrinos to be their own antiparticle. This review brings together the experimental, nuclear theory, and particle theory aspects connected to neutrinoless ββ decay to explore the path toward, and beyond, its discovery.

Probing beyond the standard model physics with double-beta decays

“…Currently, ton-scale double-β-decay experiments are under preparation with the ultimate goal of increasing the sensitivity to 0νββ-decay halflife values by two orders of magnitudes compared to current constraints, up to 10 28 years. We refer the reader to [7] for a recent review on 0νββ decay.…”

“…the Majoron or the Z 2 -odd exotic fermion, with a coupling to neutrino given by g X . 7 This is the parameter of interest we want to determine the sensitivity.…”

“…Efforts are ongoing to enhance the reliability of these calculations and evaluate their uncertainties, particularly motivated by a potential discovery of 0νββ decay in future experiments. We refer to [126] for a comprehensive review on the subject and to [7] for more recent developments in the field.…”

“…The lower limits on the half-life are converted into upper limits on the neutrino-Majoron coupling constant using equation (11a) with the axial vector coupling constant g A = 1.27 and the phase space factors from [70]. The NME calculations for the spectral index n = 1 are taken from [7] and references therein, and for n = 3 and n = 7 from [71]. competitive sensitivities can be achieved even with the relatively lower-statistics event samples that will be collected by forthcoming demonstrator experiments, such as the SuperNEMO Demonstrator (see section 5.5) or NEXT-100 (see section 5.3), or their successors (i.e.…”

Final results on the $$0\nu \beta \beta $$ decay half-life limit of $$^{100}$$Mo from the CUPID-Mo experiment

“…This raises the question of the nature of this mass. If the neutrino is its own antiparticle, a Majorana particle, then a decay mode of some nuclei would become possible, neutrinoless double beta decay (0νββ) (see reviews [3][4][5]). This decay could be observed in nuclei for which single beta decay is energetically disallowed (or disfavored by angular momentum).…”