Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 21: Weak Interaction and Fundamental Symmetries I
HK 21.1: Talk
Monday, March 16, 1998, 17:00–17:15, J
Measurement of the decay parameters in the decay of free neutrons — •Hartmut Abele1, Margarita Astruc Hoffmann1, Stefan Bae"sler1, Philipp von B"ulow1, Dirk Dubbers1, Valeri Nesvizhevsky2, Uta Peschke1, J"urgen Reich1, and Oliver Zimmer2 — 1Physikalisches Institut, Universit"at Heidelberg, Philosophenweg 12, D-69120 Heidelberg — 2Institut Laue - Langevin, Avenue des Martyrs, F-38042 Grenoble
The spectrometer PERKEO II was designed to measure neutron decay correlation coefficients. Here we present a new measurement of the beta asymmetry coefficient A. This coefficient allows us (together with a neutron lifetime measurement) to deduce the weak coupling constants from neutron decay alone. A precise knowledge of these coupling constants probes the structure of the electroweak standard model at low energies. Further, all semileptonic cross-sections used in cosmology, astrophysics and particle physics are based on these neutron decay data. Our value for A differs by three standard deviations from the value adopted by the particle data group in 1996.