title: Precision Measurement of the Radiative β Decay of the Free Neutron.
abstract: The standard model predicts that, in addition to a proton, an electron, and an antineutrino, a continuous spectrum of photons is emitted in the β decay of the free neutron. We report on the RDK II experiment which measured the photon spectrum using two different detector arrays. An annular array of bismuth germanium oxide scintillators detected photons from 14 to 782 keV. The spectral shape was consistent with theory, and we determined a branching ratio of 0.00335±0.00005[stat]±0.00015[syst]. A second detector array of large area avalanche photodiodes directly detected photons from 0.4 to 14 keV. For this array, the spectral shape was consistent with theory, and the branching ratio was determined to be 0.00582±0.00023[stat]±0.00062[syst]. We report the first precision test of the shape of the photon energy spectrum from neutron radiative decay and a substantially improved determination of the branching ratio over a broad range of photon energies.
authors.affiliation: University of Michigan, Ann Arbor, Michigan 48104, USA.|Physikdepartment, Technische Universität München, D-85748, Germany.
authors.forename: M J
authors.initials: MJ
authors.lastname: Bales
authors.affiliation: Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: R
authors.initials: R
authors.lastname: Alarcon
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Bass
authors.affiliation: University of Maryland, College Park, Maryland 20742, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Beise
authors.affiliation: University of Maryland, College Park, Maryland 20742, USA.
authors.forename: H
authors.initials: H
authors.lastname: Breuer
authors.affiliation: University of Sussex, Brighton, BN1 9QH, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Byrne
authors.affiliation: University of Michigan, Ann Arbor, Michigan 48104, USA.
authors.forename: T E
authors.initials: TE
authors.lastname: Chupp
authors.affiliation: National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Coakley
authors.affiliation: Indiana University, Bloomington, Indiana 47408, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Cooper
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Dewey
authors.affiliation: University of Kentucky, Lexington, Kentucky 40506, USA.
authors.forename: S
authors.initials: S
authors.lastname: Gardner
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: T R
authors.initials: TR
authors.lastname: Gentile
authors.affiliation: University of Kentucky, Lexington, Kentucky 40506, USA.
authors.forename: D
authors.initials: D
authors.lastname: He
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: H P
authors.initials: HP
authors.lastname: Mumm
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Nico
authors.affiliation: Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: B
authors.initials: B
authors.lastname: O'Neill
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Thompson
authors.affiliation: Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: F E
authors.initials: FE
authors.lastname: Wietfeldt