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

Thursday 24 Sept 2026, 11:00 → 12:00 Europe/Ljubljana

A/1-106 - Seminarska soba fizike (F5) (Jamova)

Neutrinoless double beta (0νββ) decay is one of the most powerful tools for probing physics beyond the Standard Model, most notably the Majorana nature of neutrinos. Extensions of this framework involving light new physics mediators, such as Majoron-like bosons, have traditionally been searched for through their contribution to missing energy, treating the new particle as invisible. In this talk, I will present a complementary and largely unexplored scenario: one in which the Majoron-like particle is produced on-shell during 0νββ decay but is massive and long-lived enough to travel a macroscopic distance before decaying into visible final states. I will discuss the resulting displaced energy depositions from decays into photon pairs, a photon plus a dark photon, and electron-positron pairs, and show how these signatures distort the expected visible energy spectra in characteristic, distance-dependent ways. These displaced-decay topologies offer novel experimental handles at current and next-generation 0νββ decay experiments, with the potential to improve sensitivity to Majoron couplings by more than two orders of magnitude relative to standard invisible Majoron searches. I will also comment on how the effective interactions responsible for this phenomenology can arise naturally in well-motivated UV completions that are otherwise inaccessible to conventional 0νββ decay searches, underscoring the value of displaced-vertex signatures as a new probe of neutrino mass generation mechanisms.