Displaced Signals from Long-lived Particles in Neutrinoless Double Beta Decay

Year: 2026

Type: preprint

Abstract: Much of the literature on neutrinoless double beta ($0νββ$) decay with light new-physics mediators focuses on invisible missing energy. We investigate the scenario in which a massive Majoron-like particle $ϕ$ is produced on-shell during $0νββ$ decay and subsequently decays into visible final states after travelling a macroscopic distance. Specifically, we analyze the displaced energy deposition from $ϕ$ decays into a photon pair ($γγ$), a photon and a dark photon ($γγ_D$) and an electron-positron pair ($e^+e^-$). We demonstrate that the displaced decays modify the expected visible energy spectra and provide novel, distinct experimental signatures at current and upcoming $0νββ$ experiments, with the promise of improving the sensitivity of the standard invisible Majoron searches in $0νββ$ decay by more than two orders of magnitude. The relevant effective couplings can naturally arise in well-motivated ultraviolet-complete scenarios that conventional $0νββ$ decay searches cannot probe.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.05352

Authors: Bolton, Patrick D., Boudjema, Noor-Inès, Deppisch, Frank F., Hati, Chandan, Majumdar, Chayan

Institutions: Jožef Stefan Institute, University College London, Universitat de València, Instituto de Física Corpuscular, Chinese Academy of Sciences, Institute of Modern Physics

Language: English

Topic: Neutrino Physics Research

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: U.S. Department of Energy, Yale University, University of Washington, Ministerio de Ciencia, Innovación y Universidades, Generalitat Valenciana, Javna Agencija za Raziskovalno Dejavnost RS, Science and Technology Facilities Council, Agencia Estatal de Investigación

OpenAlex ID: W7211885458