Precise Measurement of Muon Capture on the Proton

• Main Authors: Kammel, P, Andreev, V. A, Balin, D. V, Carey, R. M, Case, T, Chitwood, D. B, Clayton, S. M, Crowe, K. M, Deutsch, J, Debevec, P. T, Dick, P. U, Dijksman, A, Egger, J, Fahrni, D, Fetisov, A. A, Freedman, S. J, Ganzha, V. A, Gartner, B, Govaerts, J, Gray, F. E, Hartmann, F. J, Herold, W. D, Hertzog, D. W, Jatsoura, V. I, Krivshich, A. G, Lauss, B, Maev, E. M, Maev, O. E, Markushin, V. E, Onderwater, C. J. G, Petitjean, C, Petrov, G. E, Polly, C. C, Prieels, R, Sadetsky, S. M, Schapkin, G. N, Schmidt, R, Semenchuk, G. G, Soroka, M, Vorobyov, A. A, Voropaev, N. I
• Format: Journal Article
• Language: English
• Published: 12.02.2002
• Subjects: Physics - Nuclear Experiment
• DOI: 10.48550/arxiv.nucl-ex/0202011

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.