  The aim of this work is experimental discovery 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 ratio of triple to double coincidences is
connected with relative intensity of radiative neutron decay (branching ratio -
B.R.) B.R. = (3.2+1.6)10-3 (with 90 % C.L. and in the gamma energy region
greater than 35 keV), which we are the first in the world to measure during the
second and third cycles on FRMII (TUM, Germany) in Summer 2005. This value of
B.R. is consistent with standard electroweak theory.
