Precision Muon Capture on the Proton and Very Light Nuclei

1. Precision Muon Capture on the Proton and Very Light Nuclei • Peter Kammel • Department of Physics and Center for Experimental Nuclear Physics and Astrophysics, University of Washington • http://www.npl.washington.edu/muon/ MuCap MuSun INT-12-3: Light nuclei from first principles September 17 - November 16, 2012

2. Outline • m  e n n Strength of Weak Interaction • MuLanGF • m + p  n + n Basic QCD Symmetries • MuCapgP • m+ d  n + n + n Weak few nucleon reactionsm+ 3He  t+ n and astrophysics • MuSun

3. Muon Lifetime • Fundamental electro-weak couplings • Implicit to all EW precision physics • Uniquely defined by muon decay GFaMZ 9 ppm  0.5 ppm 0.37 ppb 23 ppm MuLan Collaboration Extraction of GF from tm : Recent two-loop calc. reduced error from 15 to ~0.2 ppm q QED

4. MuLanFinal Results t(R06) = 2 196 979.9± 2.5 ± 0.9 ps t(R07) = 2 196 981.2 ± 3.7 ± 0.9 ps t(Combined) = 2 196 980.3 ± 2.2 ps (1.0 ppm) The most precise particle or nuclear or atomic lifetime ever measured New GFGF(MuLan) = 1.166 378 7(6) x 10-5 GeV-2 (0.5 ppm) MuLan PRL 106, 041803 (2011) and http://arxiv.org/abs/1211.0960

5. Outline • m  e n n Strength of Weak Interaction • MuLanGF • m + p  n + n Basic QCD Symmetries • MuCapgP • m+ d  n + n + n Weak few nucleon reactionsm+ 3He  t+ n and astrophysics • MuSun

6. Muon Capture on the Proton • Historical: V-A and m-e Universality • Today: EW current key probe for • Understanding hadrons from fundamental QCD • Symmetries of Standard Model • Basic astrophysics reactions -+ p  m+ n charged current Chiral Effective Theories Lattice Calculations

7. Capture Rate LS and Form Factors • MuonCapture • Form factors - + p  m+ n rateLSat q2= -0.88 mm2 + second class currentssuppressed by isospinsymm. Lorentz, T invariance • gV, gM from CVC, e scattering • gA from neutron beta decay All form factors precisely known from SM symmetries and data. apart from gP = 8.3 ± 50% ~0.4 % 9 % pre MuCap

8. Axial Vector gA • PDG 2008gA(0)= 1.2695±0.0029 • PDG 2012gA(0)=1.2701 ±0.0025 • Future ? gA(0)=1.275 • Axial Mass • LA= 1 GeVnp, p electro production • 1.35 nuclear targets PDG12 A. Garcia

9. Pseudoscalar Form Factor gP • History • PCAC • Spontaneous broken symmetries in subatomic physics, Nambu. Nobel 2008 • State-of-the-art • Precision prediction of ChPT • Foundations for mass generation chiral perturbation theory of QCD gP = (8.74  0.23) – (0.48  0.02)= 8.26  0.23 leading order one loop two-loop <1% • gPexperimentally least known nucleon FF • solid QCD prediction (2-3% level) • basic test of QCD symmetries • required to “use” muon capture Kammel & Kubodera, Annu. Rev. Nucl. Part. Sci. 2010.60:327 Gorringe, Fearing, Rev. Mod. Physics 76 (2004) 31 Bernard et al., Nucl. Part. Phys. 28 (2002), R1

10. 45 years of Effort to Determine gP OMC RMC - + p  n +  + g Kammel&Kubodera “Radiativemuon capture in hydrogen was carried out only recently with the result that the derived gP was almost 50% too high. If this result is correct, it would be a sign of new physics... ’’ — Lincoln Wolfenstein (Ann.Rev.Nucl.Part.Sci. 2003)

11. “Rich” MuonAtomic Physics Makes Interpretation Difficult • Strong sensitivity to hydrogen density f (rel. to LH2) • In LH2 fast ppm formation, but lop largely unknown LT= 12 s-1 Lortho=506s-1 Lpara=200s-1 LS= 710 s-1

12. Precise Theory vs. Controversial Experiments gP RMC @TRIUMF ChPT OMC@ Saclay TRIUMF 2006 exp theory lOP(ms-1) • no overlap theory & OMC & RMC • large uncertainty in lOP gP  50% ?

13. MuCap Strategy • Precision technique • Clear Interpretation • Clean stops in H2 • Impurities < 10 ppb • Protium D/H< 10 ppb • Muon-On-Request • All requirements simultaneously

14. MuCap Strategy Precision technique Clear Interpretation Clean stops in H2 Impurities < 10 ppb Protium D/H < 10 ppb Muon-On-Request All requirements simultaneously • mpnn rare, only 0.16% of menn • neutron detection not precise enough Lifetime method • S= 1/- - 1/+ • measureto 10ppm

15. MuCap Strategy • Precision technique • Clear Interpretation • Clean stops in H2 • Impurities < 10 ppb • Protium D/H< 10 ppb • All requirements simultaneously At 1% LH2 density mostly pm atomsduring muon lifetime

16. MuCap Strategy • Precision technique • Clear Interpretation • Clean stops in H2 • Impurities < 10 ppb • Protium D/H< 10 ppb • All requirements simultaneously

17. MuCap Technique t e m

18. Muons Stop in Active TPC Target m- to prevent muon stops in walls(Capture rate scales with ~Z4) 10 bar ultra-pure hydrogen, 1.12% LH2 2.0 kV/cm drift field ~5.4 kV on 3.5 mm anode half gap bakeable glass/ceramic materials Observed muon stopping distribution p e- E 3D tracking w/o material in fiducial volume

19. MuCap Strategy Precision technique Clear Interpretation Clean stops in H2 Impurities < 10 ppb Protium D/H < 10 ppb Muon-On-Request All requirements simultaneously • CHUPS purifies the gas continuously • TPC monitors impurities • Impurity doping calibrates effect anodes time 2004:cN < 7 ppb, cH2O~20 ppb 2006 / 2007: cN < 7 ppb, cH2O~9-4ppb

20. Experiment at PSI pE3 beamline Kicker TPC Muon On Request Quadrupoles Separator Slit MuCap detector

21. Muon defined by TPC Signals digitized into pixels with three thresholds (green, blue, red) TPC side view Front face view Fiducial volume Fiducial volume TPC active volume TPC active volume muon beam direction transverse direction vertical direction vertical direction

22. Electron defined by Independent e-Tracker • Small, but significantinterference with m track • simple, robust track reconstruction andits verificationessential

23. Time Distributions are Consistent fittedlis constant No azimuth dependence 4/6/2012 23 Run groups Data run number (~3 minutes per run)

24. MuCap Results rates with secret offset, stat. errors only

25. Disappearance Rate l

26. Determination of LS molecular formation bound state effect MuCap: precision measurement MuLan MuCap PRL 2007

27. Error Budget

28. MuCap Final Results MuCapCollaboration,Oct 2012 e-Print: arXiv:1210.6545 [nucl-ex] • Capture Rate • LS(MuCap) = 714.9 ± 5.4stat ± 5.1systs-1 • LS (theory) = 712.7 ± 3.0gA± 3.0RCs-1 • Pseudoscalar Coupling • gP(MuCap) = 8.06 ± 0.48Ls(ex) ± 0.28Ls(th) • for gA(0)  -1.275 gP(MuCap) 8.34 recent calculations PDG12 updated Czarnecki, Marciano, Sirlincalculation

29. PreciseandUnambiguousMuCapResultVerifiesBasic Predictionof Low Energy QCD gP(MuCap) = 8.06 ± 0.55 gP(theory) = 8.26 ± 0.23

30. Outline • m  e n n Strength of Weak Interaction • MuLanGF • m + p  n + n Basic QCD Symmetries • MuCapgP • m+ d  n + n + n Weak few nucleon reactionsm+ 3He  t+ n and astrophysics • MuSun

31. Motivation μ- + d  ν + n + nmeasure rate Λdinμd() atom to <1.5% • simplest nuclear weak interaction process with precise th.& exp. nucleon FF (gP) from MuCap rigorous QCD based calculations with effective field theory • close relation to neutrino/astrophysics solar fusion reactionpp de+ νd scattering in SNO exp. • model independent connection to μd by single Low Energy Constant (LEC)

32. Quest for “unknown” Axial LEC LEC Extract from axial current reaction in • 2-body system • theoretical clean, natural progression • experimental information scarce: ~100% uncertainty in LEC • MuSun only realistic option, reduce uncertainty 100% to ~20% • 3-body system • 2 LECs and additional complexity enter • tritium beta decay • current state of the art • “Calibrate the Sun” potential current

33. Precise Experiment Needed

34. Muon Physics and Interpretation complex, can one extract EW parameters ? • Precision technique • Clear Interpretation • Clean stops in D2 • Impurities < 1ppb • H/D < 100 ppb Optimal conditions Muon-Catalyzed Fusion Breunlich, Kammel, Cohen, LeonAnn. Rev. Nucl. Part. Science, 39: 311-356 (1989)

35. Precise Experiment Possible? • Precision technique • Clear Interpretation • Clean stops in D2 • Impurities < 1ppb • H/D < 100 ppb Active muon target

36. MuSun Detector System Electron Tracker Liquid Ne Circulation CryoTPC TPC Digitizer Electronics Impurity filtering

37. Fusions in TPC run2011, prelim mSC 3He  robust muon tracking algorithm at 10-5 level required ! t+p mSC 2 ms

38. Status and Plans Analysis • analysis run 2011 data 4.8 x 109goodμ- stop 4 x 108μ+ stopevents • first physics publication • study detector upgrades Upgrades • new beamline at PSI • cryo preamp • TPC optimization • improved purity and monitoring Final runs 2013-14 Commissioning October 2012

39. m3He • Reaction • + 3He → 3H + n • Updated Results • PSI experiment: 1496±4 /s (0.3%) • Pisa-JLab theory: 1494±21 /s • gP(q2=-0.954mm2)=8.2±0.7

40. Summary: Evolution of Precision =8.06 ± 0.55 (mp)= 8.2 ± 0.7 (m3He exp+MKRSVtheo) in progress complete future complete

41. Collaborations MuLan Boston University, USA University of Illinois at Urbana-Champaign, Urbana, USA James Madison University, Harrisonburg, USA University of Kentucky, Lexington, USAKVI, University of Groningen, Groningen, The Netherlands Paul Scherrer Institute (PSI), Villigen, Switzerland Regis University, Denver, USA University of Washington, Seattle, USA MuCap/MuSun Petersburg Nuclear Physics Institute (PNPI), Gatchina, RussiaPaul Scherrer Institute (PSI), Villigen, Switzerland University of California, Berkeley (UCB and LBNL), USA University of Illinois at Urbana-Champaign, Urbana, USA University of Washington, Seattle, USA UniversitéCatholique de Louvain, BelgiumUniversity of Kentucky, Lexington, USABoston University, USA Regis University, Denver, USA University of South Carolina, USA Supported by NSF, DOE, Teragrid, PSI and Russian Academy Science