Searching for Long-Lived Particles in Free Neutron Experiments

2025/06/10 by B. Meirose, Meirose, B., R. Nieuwenhuis +9
Physics and Astronomy · #Atomic and Subatomic Physics Research #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Neutrino Physics Research #Nuclear physics research studies

paper · pdf · doi:10.48550/arxiv.2506.08701

openalex publication_date 2025/06/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We explore the decay of free neutrons into exotic long-lived particles, whose decays could be detected in the next-generation free neutron experiments. We show that such a possibility is viable as long as the exotic particle is highly mass-degenerate with the neutron, avoiding exclusion by large-volume detectors. We estimate the number of observable events and identify the most promising final states from both theoretical and experimental perspectives. Our analysis highlights the unique capability of the HIBEAM-NNBAR experiment at the European Spallation Source to probe this unexplored region of parameter space, opening a new avenue for exploring physics beyond the Standard Model. We estimate that several events per year could be observed in the NNBAR experiment.

Citations

• Search for neutral long-lived particles that decay into displaced jets in the ATLAS calorimeter in association with leptons or jets using pp collisions at √(s)=13 TeV
• The SHiP experiment at the proposed CERN SPS Beam Dump Facility
• Dinucleon and Nucleon Decay to Two-Body Final States with no Hadrons in Super-Kamiokande
• Review of Nucleon Decay Searches at Super-Kamiokande
• Review of Particle Physics

Related

• Determination of the Free Neutron Lifetime
• New generation of neutron decay experiments
• An exciting hint towards the solution of the neutron lifetime puzzle?
• Selected Aspects of Neutron Decay
• The NNbar Experiment at the European Spallation Source