2. New Precision Determination of g p and G F, the MuXperiments at PSI Bernhard Lauss University of California @ Berkeley on behalf of the MuCAP and MuLAN Collaborations EXA’05

3. Overview 1) MuLAN G F 2) MuCAP g p EXA’05

4. MuLAN Muon Lifetime Analysis MuLAN makes a precision measurement of the Positive Muon Lifetime EXA’05 Positive Muon Lifetime is closely connected to the Fermi Coupling Constant G F   e ee WW Standard Model G F is a fundamental constant of nature

5. The G F from Fermi Theory successfully describes all weak processes EXA’05 muon decay beta decay

6. additional higher order QED contributions QED radiative corrections EXA’05

7. All weak radiative corrections can be incorporated in the Standard Model ggg Re-normalize g precision EW physics via quantum loops. (probes particle spectrum / top prediction) EXA’05

8. Dominant theoretical uncertainty in muon lifetime was reduced from 16 to 0.3 ppm (2-loop ’99) ! (2-loop ’99) ! EXA’05 Recent improvement in calculations of   - Hadronic Contributions to the Muon Lifetime Timo van Ritbergen, Robin G. Stuart, Phys.Lett. B437 (1998) 201-208 - Complete 2-loop Quantum Electrodynamic Contributions to the Muon Lifetime in the Fermi Model, Timo van Ritbergen, Robin G. Stuart, Phys.Rev.Lett. 82 (1999) 488-491 - Complete O(N_f alpha 2 ) Weak Contributions to the Muon Lifetime Paresh Malde, Robin G. Stuart, Nucl.Phys. B552 (1999) 41-66 - Complete Two Loop Electroweak Contributions to the Muon Lifetime in the Standard Model M. Awramik, M. Czakon, hep-ph/0305248 - Two Loop Electroweak Bosonic Corrections to the Muon Decay Lifetime M. Awramik, M. Czakon, hep-ph/0211041 etc........

9. EXA’05 Present Experimental Situation PDG 2004 average:   = 2.19703  s (18 ppm)  G F = 1.6637 (1) GeV 2 (9ppm) single best experiment 27 ppm error   e ee WW DuclosBalandinGiovanettiBardin  Lan 03 1973 1974 1984 1984

10. EXA’05 Present Experimental Situation PDG 2004 average:   = 2.19703  s (18 ppm)  G F = 1.6637 (1) GeV 2 (9ppm) single best experiment 27 ppm error   e ee WW DuclosBalandinGiovanettiBardin  Lan 1973 1974 1984 1984 2003

11. EXA’05 Present Experimental Situation PDG 2004 average:   = 2.19703  s (18 ppm)  G F = 1.6637 (1) GeV 2 (9ppm) single best experiment 27 ppm error   e ee WW DuclosBalandinGiovanettiBardin  Lan 1973 1974 1984 1984 2003 04 expected

12. EXA’05 DuclosBalandinGiovanettiBardin  Lan goal  10  Lan goal The MuLAN experimental goal is to no longer limit the    G F extraction by experiment Need ~10 12 events 5050

13. EXA’05   e ee WW How to measure muon lifetime ?

14. The lifetime is determined by stopping muons in a target and waiting for the decay positrons. Segmented Scintillator Detector ++ e+e+ log counts time e+e+ simple slope measurement of exponential time distribution ! EXA’05

15. Using a pulsed muon beam will allow faster accumulation of statistics. ++ Time Accum. Period  in target  20x faster than dc mode Kicker 2x 75 cm plates E=0kV EXA’05 5s5s

16. Using a pulsed muon beam will allow faster accumulation of statistics. ++ Time  in target Accum. Period Measurement Period e+e+  20x faster than dc mode Kicker E=25kV EXA’05 5  s 22  s 45 ns rise/fall time new MuLAN beamline developed Kicker @ TRIUMF

17. EXA’05   e ee WW Simple slope measurement at 1ppm is not so simple anymore: The MuLAN experiment has been designed to reduce systematic errors.

18. EXA’05   e ee WW The impact of muon spin rotation (  SR) N S Front Back front-back symmetry muon beam is polarized  muon precesses in magnetic field Decay e + ’s are preferentially emitted in the direction of the μ + spin. Residual polarization effects will produce direction-dependent distortions in the μ + lifetime histograms. fit (F+B) monitor (F-B) Front Back Silver Target

19. EXA’05   e ee WW The impact of muon spin rotation (  SR) Silver - preserves muon polarization (100%) Sulfur - muon residual polarization (8%) Arnokrome-3 (AK3) (30% chromium, 10% cobalt, 60% iron) Internal Field  1 T. No observable precession frequency up to 320 MHz or =2.4 T.

20. EXA’05   e ee WW Double-Pulse Resolution - Hit Pileup detector modularity: new electronics: 174 tile pairs500 MHz wave form digitizers

21. EXA’05   e ee WW “Sneaky Muons” during beam-off period lead to time dependent background high rate (MHz), thin, fast (30 ns FWHM) wire chamber beam ~100 Gauss magnet ring to avoid influence on systematics due to muon stops in the chamber

22. EXA’05   e ee WW Online fit of 10 min of 2004 data The time scale has a secret offset - blind analysis all tile pairs different start times

23. 2004: - Setup and Test of final beam line with kicker - Finalized Detector - Accumulated 10 10 decay positrons in both targets, sulfur and AK3 - sensitive systematics comparison - used multi-hit TDCs - analysis goal: 5 ppm error 2005 - finalize and test run with WFD electronics 2006 - full 10 12 statistics for 1ppm error MuLAN Achievements and Plans EXA’05

24. MuCAP measures: μ - capture rate in ultrapure hydrogen Precision Measurement of the Singlet Muon Capture Rate on the Proton EXA’05 g W-W- νμνμ d u μ–μ– gV ud

25. EXA’05 muon decay beta decay The G F from Fermi Theory successfully describes all weak processes

26. Beta Decay (involves nucleons at low momentum) (V-A) g v = 1 g A = -1 EXA’05  -decay modified axial coupling

27. Muon Capture at higher momentum q 2 = -0.88 m   the simple (V-A) form becomes more complicated V   g V (q 2 ) + ig M (q 2 )/2M   q  + g S (q 2 )/m q  A   g A (q 2 )   + g P (q 2 ) q  /m   + ig T (q 2 )/2M   q    Muon capture involves nucleons rather than isolated quarks. The strongly- interacting substructure of the proton and neutron complicates the weak interaction physics. These complicating effects are encapsulated in the nucleonic charged-current’s four “induced form factors”: G-symmetry no second class currents EXA’05 nucleon charged current

28. Muon Capture Vector current in SM determined via CVC g V (0) = 1, g V (q 2 )=1+q 2 r 2 /6, r V 2 =0.59 fm 2 g M (0) =  p -  n +1=-3.70589 q 2 dependence from e scatt. Axial vector FF from n decay experiment g A (0)=-1.2670(35) q 2 dependence from quasi-elastic neutrino- nucleon  scattering,  e-production 2 nd class FF g S, g T forbidden by G symmetry e.g. g T /g A =-0.15 ±0.15 (exp), -0.0152 ±0.0053(QCD sum rule, up-down mass difference) error from  V ud = 0.16 % nucleon weak form factors g V,g M,g A,g P determined by SM symmetries and data contribute <0.4% uncertainty to  S g V = 0.9755(5) g M = -3.5821(25) g A = -1.245(3) remains induced pseudo-scalar g P = ? known at best only to ~ 20% EXA’05

29. Pseudoscalar Form Factor g P in Theory PCAC: g P =8.7 heavy baryon chiral perturbation theory: g P =(8.74  0.23) – (0.48  0.02) = 8.26  0.23 n  p --  g  NN FF EXA’05 - fundamental but least known weak nucleon FF - solid theoretical prediction at few percent level - basic test of chiral QCD symmetries Calculations NNLO show good convergence: 100 % 25 % 3 % delta effect small LO NLO NNLO Calculation by Fearing, Meißner et al. Ordinary muon capture on the proton can be considered an excellent testing ground for our understanding of spontaneous and explicit chiral symmetry breaking in QCD. Meißner, nucl-th/0001052 existing precise calculations are a strong motivation for a precision experiment

30. Experimental Informationon g p comes from nuclear Muon Capture Rate s EXA’05 Ordinary Muon Capture Radiative Muon Capture Yield = 10 -3 Yield = 10 -8 E PH >60MeV

31. μ –, muon capture competes with muon decay: Lifetime method avoids absolute neutron counting MuCAP Experimental Principle Comparison of Lifetimes log counts time e+e+ e – μ + lifetime = 2.19703  s  +  e + + e +  ~ Experimental goal: measure   + and   - to 10 -5 EXA’05

32. Present Experimental Situation EXA’05 g p (-0.88m 2  )

33. μ – Kinetics in Hydrogen -> Experimental Challenges  T = 12 s -1 n+ pμ ↑↓ singlet (F=0)  S = 664 s -1 n+ triplet (F=1) μ pμ ↑↑ EXA’05 strong spin dependence of V-A interaction

34. EXA’05 Present Experimental Situation EXA’05 g p (-0.88m 2  )

35. EXA’05 Present Experimental Situation EXA’05 with recent TRIUMF result on op situation even more puzzling ! g p (-0.88m 2  )

36. EXA’05 Present Experimental Situation need for a new, unambiguous precision determination EXA’05 g p (-0.88m 2  ) Mark & Dimitar please check calculation

37.   e ee WW negative muons in hydrogen pose additional problems in comparison to positive stopped muons EXA’05

38. μ – Kinetics in Hydrogen -> Experimental Challenges  T = 12 s -1 n+ Zμ Background: Wall stops and diffusion Transfer to impurities  p+Z   Z +p pμ ↑↓ singlet (F=0)  S = 664 s -1 n+ triplet (F=1) μ pμ ↑↑ EXA’05 strong spin dependence of V-A interaction ppμ para (J=0)ortho (J=1) λ op  ortho=506 s -1  para=200 s -1 molecular disturbances

39. experimental strategy Physics Unambigous interpretation At low density (1% LH 2 ) mostly capture from  p(F=0) atomic state. Clean muon stop definition: Wall stops and diffusion eliminated by 3-D muon tracking In situ gas impurity control ( goal: c Z <10 -8, c d <10 -6 /reached in 2004: c Z =7x10 -8, c d = ~2x10 -6 ) hydrogen chambers bakeable to 150º C, continuous purification TPC monitors capture on impurity and transfer to deuterium 10 -8 sensitivity with gas chromatograph  + SR: calibrated with tranverse field 70 G (saddle coil magnet around the TPC vessel) Statistics 10 10 statistics pp  P pp  O pp pp pp pp  P pp  O time (  s) 100% LH 2 1 % LH 2 10% LH 2 Experimental Challenges / MuCAP’s Solutions EXA’05

40. The Time Projection Chamber tracks muon stops in 3D. -- dT active Target = TPC - operates in proportional mode (gain ~10 4 ) - 5 - 6 kV - bakeable - quartz glass with very low thermal expansion - operates in 10 bar protium EXA’05 horizontal beam direction Anodes Strips  Stop vertical (drift time) Anodes Cathodes

41.   e ee WW EXA’05

42.   e ee WW Mucap Setup Fall 2004 EXA’05 ePCs TPC+magnet eSC hydrogen system

43. MuCap Achievements Fall 2004: - full experiment ran stably for several weeks - collected 2.5  10 9 statistics =>  s 2-3% EXA’05 (ns) Impact Parameter Cuts no cut 60 mm 30mm huge BG reduction

44.   e ee WW Careful data selection and online monitoring EXA’05

45.   e ee WW Mucap Data 2004 EXA’05

46.   e ee WW Mucap Data 2004 ONLINE: continuous monitoring of muon stopping and detector performance EXA’05 Drift Time

47.   e ee WW Mucap Data 2004 continuous monitoring of beam quality EXA’05 entering beam spot

48.   e ee WW continuous high Z cleaning system for hydrogen based on Zeolite after filling through Pd filter EXA’05 obtained 70 pbb over several weeks

49.   e ee WW We achieved gas impurity levels of 7x10 –8, as determined from real-time software analysis of impurity events, and post-run chromatography analysis. high Z purity monitoring (mainly Nitrogen, H2O) EXA’05

50. MuCap Achievements Fall 2004: - 70 ppb high-Z contamination over 5 weeks maintained - 1-2 ppm deuterium EXA’05

51. A trickier impurity: deuterium  transfer to deuterium, diffusion,  CF c d = 1ppm -> change in lifetime ~ 1ppm  p+d   d + p Ramsauer Townsend minimum in  d + p scattering at 1.6 eV Check by comparing  + and   Diffusion  -catalyzed pd fusion (Alvarez) monitors deuterium concentration  d + p  p  d   (5.3MeV)+ 3 He(0.2KeV) EXA’05 MuCAP plans to add components to directly monitor the deuterium concentration to ± 0.1ppm in liquid hydrogen, via fusion  ’s and Alvarez muons

52. MuCap Timetable Summer 2005: - additional development of the online impurity monitoring system - improvement of high-Z cleaning capacity - TPC overhaul to reach stable 5.4 kV running conditions - FADC implementation on all TPC channels - additional neutron counter for  -kinetics control ( pd , op ) Fall 2005/Spring 2006: - Planned 18 weeks of production data taking towards the final goal:  s 1% - muon on request beamline (using the MuLAN kicker) EXA’05

53. muon capture on deuteron  - + d   + n +n  to 1 % muon capture on deuteron  - + d   + n +n  to 1 % Basic EW two nucleon reaction tests effective theories and serves to calibrate v-d reactions via L 1a (SNO) Future (<2007)  D project EXA’05

54. Paul Scherrer Institute (PSI), Villigen, Switzerland University of California, Berkeley (UCB and LBNL), USA University of Illinois at Urbana-Champaign (UIUC), USA, University of Kentucky, Lexington, USA Boston University, USA James Madison University, USA KVI Groningen, Netherlands Istanbul Technical University MuLAN Collaborating Institutions MuCap EXA’05 Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia Paul Scherrer Institute (PSI), Villigen, Switzerland University of California, Berkeley (UCB and LBNL), USA University of Illinois at Urbana-Champaign (UIUC), USA Université Catholique de Louvain, Belgium TU München, Garching, Germany University of Kentucky, Lexington, USA Boston University, USA

55.   e ee WW E O P EXA’05