Magneto-$\nu$: Heavy neutral lepton search using $^{241}$Pu $\beta^-$ decays
High Energy Physics - Experiment
2026-03-05 v5 Nuclear Experiment
Abstract
The MAGNETO- experiment searches for keV-scale heavy neutral leptons (HNLs) through precise measurements of the -decay spectrum of Pu. We present spectra comprising a total of 194 million decays recorded using decay energy spectrometry with metallic magnetic calorimeters, representing the most statistically precise measurement of Pu decay to date. The -endpoint energy was determined using rays and X rays from an external Ba calibration source, yielding \,keV. The measured spectrum shows no statistically significant deviation from the allowed -decay model. From a subset of the high-statistics data, we set an upper limit on the mixing of an 11.5-keV HNL with the electron neutrino, at the 95\% confidence level.
Cite
@article{arxiv.2503.18350,
title = {Magneto-$\nu$: Heavy neutral lepton search using $^{241}$Pu $\beta^-$ decays},
author = {C. Lee and X. Zhang and A. Kavner and T. Parsons-Davis and D. Lee and N. Hines and S. T. P. Boyd and M. Loidl and X. Mougeot and M. Rodrigues and M. K. Lee and J. Song and R. Wood and I. Jovanovic and G. B. Kim},
journal= {arXiv preprint arXiv:2503.18350},
year = {2026}
}