English

First results from LEGEND-200: searching for $0\nu\beta\beta$ decay in $^{76}$Ge

High Energy Physics - Experiment 2026-03-16 v1

Abstract

The LEGEND Experiment searches for the neutrinoless double beta (0νββ\nu\beta\beta) decay of 76^{76}Ge employing active high purity germanium detectors enriched in 76^{76}Ge beyond 86%. LEGEND's experimental program is articulated in two phases: LEGEND-200, currently ongoing, and LEGEND-1000, the next generation development. LEGEND-200 started operating in 2023 at Laboratori Nazionali del Gran Sasso (LNGS) and ran in a stable physics data taking regime for about one year with 142.5 kg of detectors installed. With a target background index of 21042 \cdot 10^{-4} counts/(keV kg yr) at Qββ_{\beta\beta} \sim 2039 keV and a final exposure of 1000 kg yr, LEGEND-200 aims to reach a 3σ\sigma discovery sensitivity for a 0νββ\nu\beta\beta half-life of 102710^{27} yr. In this contribution, the LEGEND-200 experiment will be presented, with a focus on its current status and on the results obtained with the first year of data. In particular, the employed analysis routines will be introduced, the signal identification and background suppression performance will be discussed, and the background appearing in the region of interest around QββQ_{\beta\beta} will be analyzed. The performed analysis of LEGEND-200 data finds no evidence for a 0νββ\nu\beta\beta signal: a lower limit to its half-life is set instead, T1/20ν>0.51026T_{1/2}^{0\nu} > 0.5 \cdot 10^{26} yr, at 90% CL. A joint GERDA + MAJORANA Demonstrator + LEGEND-200 analysis provides a limit of T1/20ν>1.91026T_{1/2}^{0\nu} > 1.9 \cdot 10^{26} yr, at 90% CL. This work is supported by the U.S. DOE and the NSF, the LANL, ORNL and LBNL LDRD programs; the European ERC and Horizon programs; the German DFG, BMBF, and MPG; the Italian INFN; the Polish NCN and MNiSW; the Czech MEYS; the Slovak RDA; the Swiss SNF; the UK STFC; the Canadian NSERC and CFI; the LNGS and SURF facilities.

Keywords

Cite

@article{arxiv.2603.12884,
  title  = {First results from LEGEND-200: searching for $0\nu\beta\beta$ decay in $^{76}$Ge},
  author = {Giovanna Saleh},
  journal= {arXiv preprint arXiv:2603.12884},
  year   = {2026}
}

Comments

Proceedings of the European Physical Society Conference on High Energy Physics (EPS-HEP2025), 7-11 July 2025, Marseille, France