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Precision measurement of the radiative beta decay of the free neutron

Published

Author(s)

Christopher D. Bass, Maynard S. Dewey, Thomas R. Gentile, Hans Pieter Mumm, Alan Keith Thompson, M J. Bales, R. Alarcon, E J. Beise, H Breuer, Jim Byrne, T E. Chupp, Kevin Coakley, R L. Cooper, B. O'Neill, F E. Wietfeldt

Abstract

The theory of quantum electrodynamics predicts that a continuous spectrum of photons is emitted in the beta decay of the free neutron in addition to a proton, an electron, and an antineutrino. We report the first precision test of the shape of the photon energy spectrum from radiative decay and a substantially improved determination of the branching ratio. The photon spectrum was measured over three decades of energy using two different detectors arrays. An annular array of bismuth germanium oxide scintillators detected photons in the energy range of 14 keV to 782 keV. The spectral shape was consistent with theory and we determined a branching ratio of 0.00331 +/- 0.00005 [stat] +/- 0.00015 [syst]. A second detector consisting of large area avalanche photodiodes directly detected photons in the energy range of 0.4 keV to 14 keV. For this array, the spectral shape was consistent with theory and the branching ratio was determined to be 0.00567 +/- 0.00022 [stat] +/- 0.00061 [syst].
Citation
Physical Review Letters
Issue
242501

Keywords

cold neutron, fundamental symmetries, neutron decay, radiative corrections, weak interactions

Citation

Bass, C. , Dewey, M. , Gentile, T. , Mumm, H. , Thompson, A. , Bales, M. , Alarcon, R. , Beise, E. , Breuer, H. , Byrne, J. , Chupp, T. , Coakley, K. , Cooper, R. , O'Neill, B. and Wietfeldt, F. (2017), Precision measurement of the radiative beta decay of the free neutron, Physical Review Letters, [online], https://doi.org/10.1103/PhysRevLett.116.242501 (Accessed February 3, 2023)
Created June 29, 2017, Updated October 12, 2021