Geometric phases from neutron–mirror-neutron mixing in cold neutron interferometry

In this paper, we review how neutron–mirror-neutron mixing can induce a geometric phase for ordinary neutrons and how this phase can be accessed with a two-arm interferometer. By choosing different magnetic fields and suitable arm lengths, the dynamical phase difference can be canceled, so that the observed phase is directly related to the mixing. We summarize the main formulas and discuss representative regions of the neutron–mirror-neutron parameter space that can be explored with cold-neutron interferometry [A. Capolupo, G. Pisacane, A. Quaranta and F. Romeo, Phys. Dark Univ. 46 (2024) 101688].