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Precise Measurement of Muon Capture on the Proton |
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| Authors: | P Kammel V A Andreev D V Balin R M Carey T Case D B Chitwood S M Clayton K M Crowe J Deutsch P T Debevec P U Dick A Dijksman J Egger D Fahrni A A Fetisov S J Freedman V A Ganzha B Gartner J Govaerts F E Gray F J Hartmann W D Herold D W Hertzog V I Jatsoura A G Krivshich B Lauss E M Maev O E Maev V E Markushin C J G Onderwater C Petitjean G E Petrov C C Polly R Prieels S M Sadetsky G N Schapkin R Schmidt G G Semenchuk M Soroka A A Vorobyov N I Voropaev |
| Institution: | 1. University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA 2. Petersburg Nuclear Physics Institute (PNPI), Gatchina, 188350, Russia 3. Boston University, Boston, MA, 02215, USA 4. University of California Berkeley, UCB and LBNL, Berkeley, CA, 94720, USA 5. Université Catholique de Louvain, B-1348, Louvain-La-Neuve, Belgium 6. Paul Scherrer Institute, CH-5232, Villigen, Switzerland 7. Technische Universit?t München, D-85747, Garching, Germany |
| Abstract: | The aim of the μCap experiment is a 1% measurement of the singlet capture rate Λ S for the basic electro-weak reaction μ + p → n + νμ. 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 μ− in hydrogen gas and the comparison with the free μ+ lifetime. The μ− experiment will be performed in ultra-clean, deuterium-depleted H2 gas at 10 bar. Low density compared to liquid H2 is chosen to avoid uncertainties due to ppμ formation. A time projection chamber acts as a pure hydrogen active target. It defines the muon stop position in 3D and detects rare background reactions. Decay electrons are tracked in cylindrical wire-chambers and a scintillator array covering 75% of 4π. This revised version was published online in August 2006 with corrections to the Cover Date. |
| Keywords: | muon capture proton pseudoscalar form factor TPC |
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