Münster 2002 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 10: Poster Session: Nuclear Physics/Spectroscopy
HK 10.21: Poster
Tuesday, March 12, 2002, 10:30–12:45, Foyer Chemie
The Neutron Decay Spectrometer "aspect" — •S. Baeßler1, F. Glück1, J. Byrne2, M.G.D. van der Grinten2, F.J. Hartmann3, W. Heil1, G. Pezoldt3, and O. Zimmer3 — 1Institut für Physik, University of Mainz, Germany — 2School of Chemistry, Physics and Environmental Sciences, University of Sussex, Brighton, UK — 3Physik Department E18, TU München, Germany
Since recently the upper left element of the Cabbibo-Kobayashi-Maskawa-Matrix Vud can be determined from neutron decay data alone with an accuracy which is comparable to the traditional derivation from nuclear decay data. Both methods agree with each other. However, both values for Vud, together with Vus and Vub from high energy physics, violate the unitarity of the Cabbibo-Kobayashi-Maskawa-Matrix by about 2 to 3 sigma.
The neutron decay data used for this test are the neutron lifetime τn and the beta asymmetry A. Recent determinations of A are not consistent with each other. In the standard model measurements of the electron neutrino correlation coefficient a are equivalent to measurements of A, so that a new measurement of a can either solve the unitarity problem, or it can confirm it with entirely different systematics.
In this poster the spectrometer "aspectNo-dq is presented. Its purpose is to measure a with a relative accuracy of a few parts per thousand which corresponds to an improvement in A by half an order of magnitude. Details can be found in [1].
[1] O. Zimmer et al., NIM A 440 (2000) 548