Neutron lifetime puzzle and neutron–mirror neutron oscillation

Abstract

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