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Muon Capture on the Deuteron The MuSun Experiment

Muon Capture on the Deuteron The MuSun Experiment. PSI Experiment R-08-01. physics update & exp. strategy detector design with Cryo-TPC overview of 2010 runs first analysis systematics beam request 2011 plans beyond 2011 in π E1 area π E1 beam test. μd +d  dd μ  p+t+ μ.

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Muon Capture on the Deuteron The MuSun Experiment

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  1. Muon Capture on the DeuteronThe MuSun Experiment PSI Experiment R-08-01 • physics update & exp. strategy • detector design with Cryo-TPC • overview of 2010 runs • first analysis • systematics • beam request 2011 • plans beyond 2011 in πE1 area • πE1 beam test μd+d  ddμ p+t+μ Petitjean BV42, Feb 17, 2011

  2. physicsupdate μ- + d  n + n + measure rate Λd in μd() atom to <1.5 % • simplest weak process in a nucleus with precise calculations & experimentsin the near future • previous experiments: 6-10% precision, 3σ discrepancy with theory • theory: many calculations, full ChPT calculations in preparation • relation to neutrino/astrophysics • solar fusion reactionp+p  de+ • n+dscattering in SNO • model independent connection to μd capture with one single Low Energy Constant • determine this LEC in clean 2N system“Calibrate the Sun” Petitjean BV42, Feb 17, 2011

  3. recent calculations of ΛD ΛD year authors method [sec-1] 397-400 1990 Tatara,Kohyama,Kubodera SNPA 416±7 1990 Adam,Truhlik,Ciechanowicz SNPA 386 2001 Ando,Park,Kubodera,Myhrer EFT* 416±6 2009 Ricci,Truhlik,Mosconi,Smejkal SNPA/EFT* 392.0±2.3 2010 Marcucci et al. EFT* SNPA ... standard nucl. physics approach with MEC currents EFT* ... hybrid effective field theory calculations Petitjean BV42, Feb 17, 2011

  4. the Cryo-TPC liquid Neon cooling at 32K HV Cathode 80 kV drift field 11 kV/cm vertical drift 72 mm grid 3 kV cont. circulation & cleaning of the D2 gas at 5 bar density φ = 6% of liquid hydrogen 48 anode pads 90x120 mm2 Be window 0.4 mm Petitjean BV42, Feb 17, 2011

  5. experimentalstrategy • use lifetime method 1010μ→eνν decays measure τμ- to 10ppm • Λd = 1/μ- - 1/+ • low temperature ~32K D2 gas at density φ=6% spin state & hf transition observable by ddμ3He+n muon cat. fusion reaction • new high density Cryo-TPC with ultra-pure deuterium gas at 32 K • full FADC/wfd readout to cope with small signals and fusion reactions • extreme purity requirements: ≤ 1 ppb Petitjean BV42, Feb 17, 2011

  6. DAQ performance • DAQbasically taken over from MuCap & MuLan experiments • fast readout system of signals from wfd‘s, fadc‘s, etc. • event assembling – data logging - monitoring by 7 frontend PC‘s & 1 backend PC • data are collected in deadtime-free segments of ~100 ms & stored on tape ( USA) & PSI archive • daq lifetime 80% at a data rate 8 MB/sec ≈ 7500 good µ-stops/sec in TPC • independent PC‘s for control of cooling system, temperatures, pressures, etc • independent deuterium circulation/purification system (from MuCap) Petitjean BV42, Feb 17, 2011

  7. full setup of MuSun at the πE3 beamline e detector & n counters cold box lq. Neon cooling TPC wfd electronics HV D2 circulation & cleaning system Petitjean BV42, Feb 17, 2011

  8. muon beam • 25 kHz μ- flux from πE3 beamline monitored with scintillation counter (~ pileup free due to kicker) e- contamination 3-5 kHz (el.stat.sep.) • beam centering measured with 60 µm silicon detector (4 quadrants) beam was vertically a few mm off • ~50% of μ‘s are good stops in the TPC (losses not yet fully explained) • 60-70% of good μ stops are with observed decay electron 1 pixel ~ 2 mm Petitjean BV42, Feb 17, 2011

  9. overview of 2010 runs • 1) test run (3 weeks beam in May 2010): commissioning of cryo-TPC at 32K, first tests of online gas chromatography, HV at 60 kV, repaired e-detector, new n-counters, wfd electronics, new analysis software major problems: mechanical vibrations (compressor) sparks from HV → wfd trigger instabilities major success: cleaning system  c(N2) < 2 ppb  • 2) main run (8 weeks in Oct/Nov 2010): 5 weeks of stable beam production 8.3 TB μ- & 2.3 TB μ+ of clean data ≈ 5 x 109μ- and 1 x 109μ+ good TPC stops with decay electron TPC was operated stable at 80 kV all detectors worked fine successful online gas chromatography Petitjean BV42, Feb 17, 2011

  10. TPCsignals • TPC has 48 pads with area 120 x 90 mm2 vertical drift HV-cath. to grid 72 mm • forced trigger produces waveform of all pads within full drift time (16 µs) • event display in forced trigger mode  (in yellow Gaussian fits to a muon track) • normal operation mode with wfd‘s in self triggering mode above given theshold • event display showing μ track in TPC  in yellow Gaussian fits Petitjean BV42, Feb 17, 2011

  11. onlinedisplay μ→ 1 pad = 15x17 mm2 Petitjean BV42, Feb 17, 2011

  12. electrontime spectratime = t(eSC) – t(μSC) with / w.o. TPC stop requirement μ- beam simple scint. trigger shows short-lifed component of wall stops green curve: TPC stop reqirement μ+ beam pure exponential even without TPC stop requirement ! Petitjean BV42, Feb 17, 2011

  13. muon catalyzedfusion events – ranges R main fusion channels in D2 at φ=6% • ddμ →3He(0.82 MeV) + μ + n(2.5 MeV) R3He = 0.18 mm w = 88% →3Heμ(0.80 MeV) + n(2.5 MeV) R3Heμ = 0.6 mm w = 12% • ddμ →p(3.0 MeV)+ t(1.0 MeV) + μ Rp = 16 mm Rt = 1 mm ~ 6% fusion events per muon background channel if hydrogen present • dμ+p→pdμ→3Heμ + γ(5.5 MeV) 85% →3He(0.2 MeV) +μ(5.3 MeV)15% „Alvarez muons“ Rμ ~23 cm ! ~ 0.1% Alvarez events per muon (if cp = 0.2%) causing ∆ΛD ~ 45 Hz cp < 0.01% required ddμ → p + t + μ event ddμ →3He + n + μ Petitjean BV42, Feb 17, 2011

  14. study of μ-stops at higher gas densitiesS-energy = 2 x Eμ(second last anode) + Eμ(stop anode) Petitjean BV42, Feb 17, 2011

  15. gas chromatography: isotopic purity ~ 0.2% Petitjean BV42, Feb 17, 2011

  16. N2 impurity analysis ≤ ppb levelby online gas chromatography Petitjean BV42, Feb 17, 2011

  17. some problems during the main run left: ~1 kHz mechanical vibrations induced by the compressor right: reduction of vibration effect by electronic filtering ~1 Hz of sparks from 80 kV induced by charge-up of insulators inside the vacuum chamber of the TPC preliminary solution: cut out time sections near and after sparks <Δt~10μs> Petitjean BV42, Feb 17, 2011

  18. work plan & beam request 2011 • workplan for April – June 2011 (in experimental hall) • reassemble isotope separator using the TPC refrigeration system and deplete deuterium inventory (5 m3) from HD gas: cp ~ 0.002  << 0.0001 • Cryo-TPC system: improve the 80 kV HV leads in the high vacuum part  avoid (or at least reduce) effects of sparking • install gold plated MACOR pad plane and new grid ( kill scattered μ stops, reduce vibrations) • clean the circulation system, test a new impurity concentration system (ICS) • replace aging preamplifier cards of electron wire chamber system • improve DAQ & electronics to handle up to 15 MB/s & reduce comp. deadtime • introduce modern FPGA electronics • beamtime request • 12 weeks (= 3 beam cycles) from June-20 – September-23, 2011 at the πE3 standard MuSun beam line with vertical separator & kicker Petitjean BV42, Feb 17, 2011

  19. future of MuSun (beyond 2011) at πE1& request conc. πE1 area • to exploit MuSun to its full potential we need beyond 2011 a low-E negative muon beam of equivalent quality as πE3, including kicker • the only available area with such potential is πE1 • since no reliable data about low energy μ- beams in πE1 were available, an ETH/PSI team made last Sept. a beam test which produced very encouraging results (next slide) • still: to realize a setup comparable to πE3 the area needs to be extended into the NEB area (which is no more in use) • thus, we request that PSI enlarges during year 2012 the πE1 area space toward the low energy area NE-B, such that it will suit future low energy muon experiments in particle physics Petitjean BV42, Feb 17, 2011

  20. measured PiE1 muon intensitiesby A. Antognoni, A. Papa, D. Ries & C.P. (ETHZ-PSI) I(40 MeV/c) = 2 x 105 s-1(negative muons)with 3.7% FWHM momentum bite I(27 MeV/c) = 6 x 106 s-1(positive muons)with 3.7% FWHM momentum bite electron contaminationwithout separator: 200 / 1 (electrons / muons) electron contaminationwithseparator: < 0.5 / 1 (not measurable) □ vertical profile is asymmetric because of the half-quadrupoles □ horizontal profile is Gaussian and in agreement with simulations □ profile do not depend on momentum bite Petitjean BV42, Feb 17, 2011

  21. conceivable layout of πE1 area for MuSun πE1 2 3 1 4 1 spinrot II2 kicker3 slits4 MuSun exp. Petitjean BV42, Feb 17, 2011 Seite 21 PSI, PSI, 23. September 2014 23. September 2014

  22. end of presentation

  23. πE1 area during beam test Seite 23 PSI, PSI, 23. September 2014 23. September 2014

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