Search for neutron–mirror neutron oscillations in a laboratory experiment with ultracold neutrons

Mirror matter is considered as a candidate for dark matter. In connection with this an experimental search for neutron–mirror neutron (nn′) transitions has been carried out using storage of ultracold neutrons in a trap with different magnetic fields. As a result, a new limit for the neutron–mirror neutron oscillation time τosc has been obtained, τosc≥448 s (90% C.L.), assuming that there is no mirror magnetic field larger than 100 nT. Besides a first attempt to obtain some restriction for mirror magnetic field has been done.