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MuCap

MuCap. High-Precision Measurement of Muon Capture on the Proton. m. BVR35 Progress report presented by Claude Petitjean, PSI 12 Febuary 2004. http://www.npl.uiuc.edu/exp/mucapture/. MuCap Experiment. experimental goal principle of measurement apparatus time projection chamber (TPC)

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MuCap

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  1. MuCap High-Precision Measurement of Muon Capture on the Proton m BVR35 Progress report presented by Claude Petitjean, PSI 12 Febuary 2004 http://www.npl.uiuc.edu/exp/mucapture/

  2. MuCap Experiment • experimental goal • principle of measurement • apparatus • time projection chamber (TPC) • data from run in fall 2003 • some results • milestones reached in 2003 • upgrades for run in fall 2004 • Beam request 2004

  3. MuCap collaboration V.A. Andreev, A.A. Fetisov, V.A. Ganzha, V.I. Jatsoura, A.G. Krivshich, E.M. Maev, O.E. Maev, G.E. Petrov, G.N. Schapkin, G.G. Semenchuk, M. Soroka, A.A. Vorobyov Petersburg Nuclear Physics Institute (PNPI), Gatchina 188350, RussiaP.U. Dick, A. Dijksman, J. Egger, D. Fahrni, M. Hildebrandt, A. Hofer, L. Meier, C. Petitjean, R. Schmidt Paul Scherrer Institute, PSI, CH-5232 Villigen, SwitzerlandT.I. Banks,T.A. Case, K.M. Crowe, S.J. Freedman, F.E. Gray, B. Lauss University of California Berkeley, UCB and LBNL, Berkeley, CA 94720, USA K.D. Chitwood, S.M. Clayton, P.T. Debevec, D. W. Hertzog, P. Kammel, B. Kiburg, R. McNabb, F. Mulhauser, C. J. G. Onderwater, C. Ozben, C.C. Polly, A. Sharp, D. Webber University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA L. Bonnet, J. Deutsch, J. Govaerts, D. Michotte, R. PrieelsUniversité Catholique de Louvain, B-1348 Louvain-La-Neuve, Belgium R. M. Carey. J. Paley Boston University, Boston, MA 02215, USA T. Gorringe, M. Ojha, P. Zolnierzcuk University of Kentucky, Lexington, KY 40506, USA F.J. Hartmann Technische Universität München, D-85747 Garching, Germany mCap

  4. a 1% measurement of Λs determines gp – the “weak nucleonic charged current induced pseudoscalar form factor” – to < 7%precision. The QCDprediction (Heavy Baryon Chiral Pert. Theory) is ~2% precise. Experimental goal measure the rateΛsofmuon captureon the proton to 1%precision. Muon capture is a semileptonic weak interaction process, and occurs predominantly from the hyperfine singlet atomic bound state.

  5. problem of previous experiments m interpretation of rate LS due to formation of ppμ molecules in lq hydrogen and badly known rate lOP of ortho-para transitions LS LT pm pm n+n F=0 F=1 Lortho ppm n+n J=1 lOP Lpara ppm n+n J=0

  6. interpretation of gP vslOP Muon Capture and gP gP update from Gorringe & Fearing RMC ChPT mCapproposed OMC Saclay New TRIUMF exp Saclay exp theory ---------o--------- lOP (ms-1)

  7. Experimental Technique For μ–, muon capture competes with muon decay: “Lifetime” Method This rate decreases the observed μ– lifetime from the vacuum lifetime, which we measure separately with μ+ : Thus we need 10 ppm measurements of theμ+/- lifetimes or a statistics of at least 1010 for both μ-decays

  8. Experimental Technique Since our experiment can only observe e+ and e– decay products, muon capture produces a small downward deflection of the μ– lifetime curve from the μ+ “vacuum” lifetime curve : log(counts) μ+ μ – “Lifetime” or “Disappearance” Method time The capture rate is easily calculated from the measured lifetimes:

  9. Technical tasks of MuCap experiment tasksgoals to be reached • ultra-clean 10-bar hydrogen gas target 0.01 ppm Z>1 impurities • deuterium depleted hydrogen („protium“) < 1 ppm deuterium • 100% stop identification no wall stops  TPC • clean electron identification & tracking 2 cylindrical wire chambers • unique μ e decay assignment μ-stop – e-vertex matching • high data rate 30 kHz μ stops • high statistics > 1010 events for μ+andμ- • μSR under control for μ+ 50-100 Gauss magnetic field

  10. Muon Detectors Experimental Setup – Apparatus TPC μPC1 μSC μPC2 μ beam ePC1 Electron Detectors ePC2 eSC (Hodoscope) • e-detectors cover 75% of 4π

  11. assembly/tests: March-Aug 2003 data-taking: Sept-Oct 2003

  12. TPC design drawing with glass frames and ceramic structure bakeable to 130 C Ucathodes = 5-6 kV E = 2 kV/cm - vdrift = 0.5 cm/μs sensitive volume (12 x 15 x 30) cm3

  13. Online display ofμ beam, μstops in TPC and e in ePC1 ePC1/eSC(phi,z)

  14. event display of muon stops& electrons

  15. event display of μ stop + impurity capture

  16. development of impurities during the 2 good data weeks full scale 1 ppm

  17. summed decay time spectra showing pile-up suppression

  18. μ– decay time spectra of 1 week with clean protium filling

  19. MuCap 2003: exponential fits to each eSC counter pair

  20. MuCap 2003:μSR enhanced fit ofμ+ decay time spectra

  21. milestones 2003 • protium production with < 0.5 ppm deuterium • ultra-clean protium gas filling (< 0.1 ppm impurities) – after installation of a new Palladium filter • newTPC@4.8 kV stable operation (perfect μ stopdetector!) • full e detector consisting of ePC1 and eSC • new frontend electronics for ePC1 • new compressor electronics for deadtime free ePC1 data collection • new DAQ running with 4 MB/s data rate (80% duty cycle) • new μSR magnet with ~50 Gauss field • new slow control system • full electronics for TPC, wire chambers and plastic counters • collimated muon beam injection system • analysis software in mature development

  22. upgrades for 2004 • protium: maintain< 0.5 ppm deuterium& < 0.1 ppm Z>1 impurities • new gas circulation, cleaning & diagnostics (Gatchina) • e-detector: include new ePC2 ( vertex tracking) • tune TPC to 5.5 kV ( online control of μd diffusion) • new0.5 mm Beryllium window ( increase good μ stops x 2) • μ-detectors: new outside μPC1&2 ( reduce μ-absorption/range-tails) • μ-beam: new tune in πE3 area ( < 3% momentum spread) • new spare TPC from Gatchina ( >6 kV to see e tracks) • upgrade DAQ for larger data flow ( ~100% duty cycle) • upgrade μSR magnet with Alu coils ( reduce scattering of e) • new online data analysis goal for 2004: collect a significant part of 1010 pileup-protected good μ-decays for μ+and μ-

  23. protium gas circulation and purifying system (Gatchina)

  24. MCstudy of μ stop distributions for various beam windows

  25. MuCap experiment:time plans of upgrades for 2004 run

  26. MuCap experiment: beam request for 2004 In 2004 we hope to approach closely the goal formulated in the proposal: a measurement of theμp singlet capture rate to ± 1% accuracy To accomplish this goal, we need area πE3 for the following activities: • setup of beamline with el.stat. separator, assemble full apparatus and electronics, test all components in the beam: 2 weeks • tune new 35 MeV/c muon beam: 1 week • test & optimize complete detector with beam: 1 week • data production towards 1010 good μ- & μ+ decays: 2 x 2.5 weeks • contingency for beam losses or other failures 1 week  we request 10 weeks in area πE3 (preferably in Oct-Dec 2004, at the end of the 2004 production cycle)

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