Measuring the proton spectrum in neutron decay-Latest results with aSPECT

M. Simson, F. Ayala Guardia, S. Baeßler, M. Borg, F. Glück, W. Heil, I. Konorov, G. Konrad, R. Muñoz Horta, K. K.H. Leung, Yu Sobolev, T. Soldner, H. F. Wirth, O. Zimmer

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The retardation spectrometer aSPECT was built to measure the shape of the proton spectrum in free neutron decay with high precision. This allows us to determine the antineutrino electron angular correlation coefficient a. We aim for a precision more than one order of magnitude better than the present best value, which is Δ a / a = 5 %. In a recent beam time performed at the Institut Laue-Langevin during April/May 2008 we reached a statistical accuracy of about 2% per 24 h measurement time. Several systematic effects were investigated experimentally. We expect the total relative uncertainty to be well below 5%.

Original languageEnglish
Pages (from-to)203-206
Number of pages4
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number2-3
StatePublished - 1 Dec 2009


  • Cabibbo-Kobayashi-Maskawa matrix
  • Neutron decay


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