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Title: Do neutrons oscillate into antineutrons?
Plain: Some theories allow a neutron to turn into its own antiparticle, changing baryon number by two. This would not show up in proton decay searches.
Precise: Search for $\Delta B = 2$ neutron-antineutron oscillations with free-neutron oscillation time $\tau_{\mathrm{nnbar}} > 8.6e7\,\mathrm{s}$ (ILL, 1994) and bound-neutron limits converting to $\sim 4.7e8\,\mathrm{s}$ (Super-Kamiokande, 2021). An answer is a detection or a free-neutron limit improved by 1 to 3 orders of magnitude.
Settled by: The proposed NNBAR experiment at the European Spallation Source and bound-neutron searches in DUNE and Hyper-Kamiokande.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: (empty)
Posed since: 1970