Are neutrinos Majorana? Fixed-target and high-energy astrophysical searches decide
Abstract
The original version of this paper proposed a new approach to determining whether neutrinos are Dirac or Majorana fermions, a fundamental open question in particle physics. Conventional searches rely on neutrinoless double beta decay, but this electron-only channel suffers from blind spots. We propose a new, complementary probe to overcome this limitation. A heavy neutral lepton (HNL) triggers a high-energy shift in how the active neutrino flavors (νe, νμ, ντ) mix---but only if the neutrinos are Majorana. For GeV-scale HNLs, the upcoming beam-dump experiment SHiP can discover the HNL and measure how it mixes with the active flavors.However, the proposed signature of the Majorana nature of neutrinos does not exist. The reasons are explained here. The analysis has been superseded by Ref.~\cite{Barenboim:2026udr}. The original version is retained as v1 for the record.
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BibTeX
@misc{barenboim2026neutrinos,
title = {{Are neutrinos Majorana? Fixed-target and high-energy astrophysical searches decide}},
author = {Gabriela Barenboim and Mauricio Bustamante and Qinrui Liu},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2606.17132},
eprint = {2606.17132},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.17132},
}
RIS
TY - UNPB
TI - Are neutrinos Majorana? Fixed-target and high-energy astrophysical searches decide
AU - Gabriela Barenboim
AU - Mauricio Bustamante
AU - Qinrui Liu
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2606.17132
UR - https://arxiv.org/abs/2606.17132
AB - The original version of this paper proposed a new approach to determining whether neutrinos are Dirac or Majorana fermions, a fundamental open question in particle physics. Conventional searches rely on neutrinoless double beta decay, but this electron-only channel suffers from blind spots. We propose a new, complementary probe to overcome this limitation. A heavy neutral lepton (HNL) triggers a high-energy shift in how the active neutrino flavors (ν_e, ν_μ, ν_τ) mix---but only if the neutrinos are Majorana. For GeV-scale HNLs, the upcoming beam-dump experiment SHiP can discover the HNL and measure how it mixes with the active flavors.However, the proposed signature of the Majorana nature of neutrinos does not exist. The reasons are explained here. The analysis has been superseded by Ref.~\cite{Barenboim:2026udr}. The original version is retained as v1 for the record.
ER -