Observation of the neutron radiative decay

The aim of this work is experimental observation and research of a rare neutron mode, the radiative beta-decay, where a new particle, the radiative gamma-quantum, is formed along with the expected decay products beta-electron, recoil proton and antineutrino. The discovery of this rare neutron decay mode was conducted through identification of triple coincidences events: simultaneous registration of beta electron, proton and radiative gamma-quantum. The ordinary neutron decay was registered by double coincidences of beta electron and recoil proton. The statistics collected allow one to deduce the branching ratio (BR) $\mathrm{BR}=(3.2\pm1.6)\cdot10^{-3}$ (90% C.L.) in the gamma energy region greater than 35 keV. This value of BR is consistent with standard electroweak theory.