Abstract
We consider a possible neutron–antineutron (n−n¯) oscillation experiment at the PF1B instrument at Institut Laue Langevin. It can improve the best existing constraint on the transition rate and also allow the testing of the methods and instrumentation which would be needed for a later larger-scale experiment at ESS. The main gain factors over the most competitive experiment, performed earlier at PF1 instrument at ILL, are: a more intense neutron beam and a new operating mode based on coherent n and n¯ mirror reflections. The installation of such an experiment would need a temporary replacement of the existing ballistic neutron guide by a specially designed n/n¯ guide with a gradually increasing cross section and a specially selected coating as well as the development and construction of an advanced n¯ annihilation detector with a high efficiency and low background. The overall gain factor could reach up to an order of magnitude and depends on the chosen experiment configuration.
Highlights
An observation of neutron–antineutron oscillations (n − n) would be a major scientific discovery with fundamental implications for particle physics and cosmology
The conservation of which is intimately associated with its role within the Abelian gauge theory of electromagnetism, there is no experimental evidence for any similar gauge interaction associated with baryon number, which would automatically lead to baryon number conservation
If the sphaleron dynamics expected from the Standard Model are a feature of nature, they can erase any baryon number violation from high energy scale processes of the type expected by dimensional analysis from the ∆B = 1 operators responsible for proton decay
Summary
An observation of neutron–antineutron oscillations (n − n) would be a major scientific discovery with fundamental implications for particle physics and cosmology This process would violate baryon number (B) by two units. If the sphaleron dynamics expected from the Standard Model are a feature of nature, they can erase any baryon number violation from high energy scale processes of the type expected by dimensional analysis from the ∆B = 1 operators responsible for proton decay. Such an experiment could take place before and would be complementary to the proposed HIBEAM/NNBAR program of neutron conversion searches at the European Spallation Source [13], at which an ultimate improvement of sensitivity to neutron–antineutron oscillations of three orders of magnitude compared to the last search with free neutrons [14] is expected. Symmetry 2021, 13, 2314 efficient enough to satisfy the “quasi-free” condition, which means that the probability of n − noscillations is not suppressed
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