Erlangen 2026 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 22: Structure and Dynamics of Nuclei VI

HK 22.3: Talk

Wednesday, March 18, 2026, 14:45–15:00, AM 00.021

Searching for signatures of the possible resonant neutrinoless double electron capture in ¹⁵²Gd at the Felsenkeller shallow-underground laboratory — •Lars Rudert, Björn Lehnert, Steffen Turkat, and Kai Zuber — TU Dresden

The hypothesized Majorana nature of neutrinos is a key motivation for many large-scale research projects in contemporary particle physics. While neutrinoless double-beta decay plays a central role in the experimental search for this property, double electron capture (ECEC) has gained increasing attention as an alternative probe. The two-neutrino mode of ECEC was first experimentally observed in 2019 by the XENON1T collaboration in ¹²⁴Xe. However, the observation of neutrinoless double electron capture remains an open experimental challenge.

A long-term measurement is currently being conducted using a ¹⁵²Gd-enriched gadolinium oxide sample, which is considered the most promising candidate for a resonance-enhanced neutrinoless double electron capture. This contribution focuses on an experiment employing an ultra-low-background well-type HPGe detector at the Felsenkeller shallow-underground laboratory, operated by the Nuclear Physics group at TU Dresden. During the ongoing measurement campaign, further optimizations of the background sensitivity are being performed and are currently under discussion. This includes an extended characterization of the detector with respect to the expected X-ray emissions from the theoretical decay.

Keywords: electroncapture; low-background