(eng)
The aim of the MuCap experiment is a 1% measurement of the singlet capture
rate Lambda_S for the basic electro-weak reaction mu + p -> n + nu_mu. This
observable is sensitive to the weak form-factors of the nucleon, in particular
to the induced pseudoscalar coupling constant g_P. It will provide a rigorous
test of theoretical predictions based on the Standard Model and effective
theories of QCD. The present method is based on high precision lifetime
measurements of mu^- in hydrogen gas and the comparison with the free mu^+
lifetime. The mu^- experiment will be performed in ultra-clean,
deuterium-depleted H_2 gas at 10 bar. Low density compared to liquid H_2 is
chosen to avoid uncertainties due to ppmu formation. A time projection chamber
acts as a pure hydrogen active target. It defines the muon stop position in 3-D
and detects rare background reactions. Decay electrons are tracked in
cylindrical wire-chambers and a scintillator array covering 75% of 4 pi.
Comment: Int. RIKEN Conf. on Muon Catalyzed Fusion and Related Exotic Atoms,
April 2001, Shimoda, Japan, to be published in Hyperfine Interactions
Prieels, René
