spontaneously mix in a process much faster than the neutron β-decay. Two groups have
performed a series of experiments in search of neutron–mirror-neutron (n− n′) oscillations.
They reported no evidence, thereby setting stringent limits on the oscillation time τ nn′.
Later, these data sets have been further analyzed by Berezhiani et al.(2009–2017), and
signals, compatible with n− n′ oscillations in the presence of mirror magnetic fields, have …