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

@misc{bolton2026displaced,
  title = {{Displaced Signals from Long-lived Particles in Neutrinoless Double Beta Decay}},
  author = {Patrick D. Bolton and Noor-Inès Boudjema and Frank F. Deppisch and Chandan Hati and Chayan Majumdar},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.05352},
  eprint = {2609.05352},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.05352},
}

TY  - UNPB
TI  - Displaced Signals from Long-lived Particles in Neutrinoless Double Beta Decay
AU  - Patrick D. Bolton
AU  - Noor-Inès Boudjema
AU  - Frank F. Deppisch
AU  - Chandan Hati
AU  - Chayan Majumdar
PY  - 2026
DA  - 2026/09/04
PB  - arXiv
DO  - 10.48550/arxiv.2609.05352
UR  - https://arxiv.org/abs/2609.05352
AB  - 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.
ER  -