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The European Physical Journal A

, Volume 38, Issue 1, pp 17–26 | Cite as

First measurements with the neutron decay spectrometer a SPECT

  • S. Baeßler
  • F. Ayala Guardia
  • M. Borg
  • F. Glück
  • W. Heil
  • G. Konrad
  • I. Konorov
  • R. Muñoz Horta
  • G. Petzoldt
  • D. Rich
  • M. Simson
  • Yu. Sobolev
  • H. -F. Wirth
  • O. Zimmer
Regular Article - Experimental Physics

Abstract

The neutron decay spectrometera SPECT has been built to perform a precise measurement of the proton spectrum shape in the decay of free neutrons. Such a measurement allows a determination of the neutrino electron angular-correlation coefficienta . The present best experiments have an uncertainty of Δa/a = 5% and since the seventies there is no substantial improvement. Witha SPECT, we aim for an uncertainty which is lower by more than an order of magnitude, thus enabling us to perform several precise tests of the Standard Model. In our first beam time at the particle physics beam MEPHISTO at the Forschungsneutronenquelle Heinz Maier-Leibnitz, we studied the properties of the spectrometer. The most serious problem turned out to be the situation- and time-dependent behavior of the background. From the data sets from this beam time in which a background problem was not obvious, we could extract a value ofa = - 0.1151±0.0040stat , but we could not quantify the background uncertainty. We show ways to deal with the background and other problems for future beam times.

PACS

23.40.Bw Weak-interaction and lepton (including neutrino) aspects 13.30.Ce Leptonic, semileptonic, and radiative decays 12.15.Hh Determination of Kobayashi-Maskawa matrix elements 

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Copyright information

© SIF, Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • S. Baeßler
    • 1
  • F. Ayala Guardia
    • 1
  • M. Borg
    • 1
  • F. Glück
    • 2
    • 5
  • W. Heil
    • 1
  • G. Konrad
    • 1
  • I. Konorov
    • 3
  • R. Muñoz Horta
    • 1
  • G. Petzoldt
    • 3
  • D. Rich
    • 4
  • M. Simson
    • 3
  • Yu. Sobolev
    • 1
  • H. -F. Wirth
    • 3
  • O. Zimmer
    • 3
  1. 1.Institut für PhysikUniversität MainzMainzGermany
  2. 2.Universität Karlsruhe (TH)IEKPKarlsruheGermany
  3. 3.Technische Universität MünchenPhysik-DepartmentGarchingGermany
  4. 4.Forschungsneutronenquelle Heinz Maier-LeibnitzGarchingGermany
  5. 5.Research Institute for Nuclear and Particle PhysicsTheory DepartmentBudapest 114Hungary

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