Radiative decay of the free neutron

Abstract

The theory of quantum electrodynamics predicts that beta decay of the neutron into a proton, electron, and antineutrino should be accompanied by a continuous spectrum of soft photons. We recently reported the first observation of this radiative decay mode of the neutron, measured by recording photons in coincidence with both the electron and proton emitted in neutron decay. The experiment was performed on the NG-6 Fundamental Physics Beam Line at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). A new experiment is under development to measure both the branching ratio and energy spectrum for radiative decay with a relative standard uncertainty of a few percent. We briefly review the fundamental neutron physics program at the NCNR and describe the new radiative decay experiment. © 2007 American Institute of Physics.