Neutron lifetime puzzle and neutron–mirror neutron oscillation

Abstract

Standard Model, with its present precision, predicts the neutron β-decay time τSM=878.7±0.6 s which is perfectly compatible with the neutron lifetime measured in the trap experiments τtrap=879.4±0.6 s. However, the lifetime measured in the beam experiments via counting the protons produced by β-decay n→peν¯e, τbeam=888±2.0 s, is deviated from τSM by 9 seconds (4.4σ). This discrepancy can be explained via the neutron n conversion into mirror neutron n', its dark partner from parallel mirror sector. Provided that n and n' have a tiny mass splitting ∼10-7 eV, in magnetic fields of few Tesla used in beam experiments, n-n' transition is resonantly enhanced converting a 1% fraction of neutrons into mirror neutrons which decay in invisible mode n'→p'e'ν¯e'. Thus less protons are produced and the measured value τbeam appears larger than the true decay time τSM=τtrap.