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Peter Kammel

Muon Capture in Hydrogen. Peter Kammel. Session in Honor of the 60 th Birthday of W.-Y. Pauchy Hwang. Outline. m + p  n + n m + 3 He  3 H + n m + d  n + n + n m  e + n e + n m. Basic QCD Symmetries. MuCap. “Calibrating the Sun ”. MuSun. G F.

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Peter Kammel

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  1. Muon Capture in Hydrogen Peter Kammel Session in Honor of the 60th Birthday of W.-Y. Pauchy Hwang

  2. Outline • m + p  n + n • m + 3He  3H + n • m + d  n + n + n • m  e + ne + nm Basic QCD Symmetries MuCap “Calibrating the Sun” MuSun GF MuLan

  3. 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 Lattice CalculationsChiral Effective Theories

  4. PR C16 (1977) 397 Form Factors and gP - + p  m+ n rateLSat q2= -0.88 mm2 • Muon Capture • Form factors + second class currentssuppressed by isospin symm. Lorentz, T invariance All form factors precisely known from SM symmetries and data. CVC, n beta decay apart from gP = 8.3 ± 50%

  5. NobelLecture2008 "the discovery of the mechanism of spontaneous broken symmetry in subatomic physics." Foundations for mass generation chiral perturbation theory of QCD

  6. Pseudoscalar Form Factor gP gP determined by chiral symmetry of QCD: gP = (8.74  0.23) – (0.48  0.02) = 8.26  0.23 ChPT leading order one loop two-loop <1% • gP basic and experimentally least known nucleon form factor • solid QCD prediction (2-3% level) • basic test of QCD symmetries • recent lattice results T. Gorringe, H. Fearing, Rev. Mod. Physics 76 (2004) 31V. Bernard et al., Nucl. Part. Phys. 28 (2002), R1

  7. 45 Years of Experiments to Determine gP • - + p  m+ n OMC BR~10-3 • 8 experiments, typical precision 10-15%, Saclay 4%, but interpretation? • - + p  m+ n + g RMCBR~10-8, E>60 MeV • - + 3He  m+ 3H • Muon Capture Correlations in Nuclei • p electro-production PR C22 (1980) 233 … 279 ± 25 eventsBRg(k>60MeV) = (2.10 ± 0.21) x 10-8 2008

  8. Brief Digression m + 3He → 3H + n rad. corr.

  9. m+p Results before MuCap OMC RMC LH2 LH2 LH2 LH2 GH2 GH2 LH2 LH2 “ Radiative muon 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)

  10. 1 % LH2 Lortho=506s-1 100% LH2 pm f λppm ppμ ppmO ppμ pm ppmO ppmP ppmP time (ms) “Rich” Muon Atomic Physics makes Interpretation Difficult ! LT= 12 s-1 triplet (F=1) pμ↑↑ Lpara=200s-1 λop μ para (J=0) ortho (J=1) pμ↑↓ • Interpretation requires knowledge of ppm population • Strong dependence on hydrogen density f singlet (F=0) LS= 710s-1 n+n

  11. Precise Theory vs. Controversial Experiments gP - + p  m+ n @ Saclay - + p  m+ n + g@TRIUMF ChPT mCapprecisiongoal TRIUMF 2006 exp theory lOP(ms-1) • no overlap theory & OMC & RMC • large uncertainty in lOP gP  50% ?

  12. MuCap Experimental Strategy • Lifetime method • 1010m→enn decays • measure - to 10ppm, • S = 1/- - 1/+to 1% • Unambiguous interpretation at low target density • Clean m stop definition in active target (TPC) • Ultra-pure gas system and purity monitoring at 10 ppb level • Isotopically pure “protium” (10 ppb) m → enn LSreduces lifetime by 10-3 + log(counts) - μ+ μ – te-tm fulfill all requirements simultaneouslyunique MuCap capabilities

  13. MuCap Detector @ PSI

  14. m- Muons Stop in Active TPC Target 10 bar ultra-pure hydrogen, 1.16% 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 E p e- 3D tracking w/o material in fiducial volume

  15. 6 mm Inside TPC Time Spectra m-e impact parameter cut huge background suppression diffusion (deuterium) monitoring blinded master clock frequency variety of consistency checks

  16. Ls and gP Results 07 with + from PDG and MuLan • MuCap Result 07 • Theory 07 • Pseudoscalar coupling from MuCap 07 SMuCap = 725.0  13.7stat 10.7sys s-1 PRL 99, 032001 (2007) further sub percent theory required Average of HBChPT calculations of S: STheory = 710.6 s-1 Apply new rad. correction (2.8%): Czarnecki, Marciano,Sirlin , PRL 99 (2007) gP = 7.3 ± 1.1

  17. gP Landscape after MuCap 07 - + p  m + n + g • first precise and unambigous determination of gP = 7.3 ± 1.1 • clarification of long-standing puzzle in QCD and chiral dynamics • final analysis of full data should 3x improve precision

  18. Ongoing Final Analysis should lead to a 3-fold improved Precision • Many hardware upgrades (readout, purification, kicker) • 10x higher statistics Final Precision of gP determination Watch new tn experiments: gA to explain Serebrov et al.would shift predictedLS by ~ 0.7 % MuCap final 09? dgP MuCap 07 + dRC + dgA exp dLS/LS

  19. Outline • m + p  n + n • m + 3He  3H + n • m + d  n + n + n • m  e + ne + nm

  20. Motivation • m- + d  n + n + nRateLd from md() atom • MeasureLdto < 1.5 % • Simplest weak interaction process in a nucleusallowing for precise theory & experiment • Close relation to neutrino/astrophysics • Broader Impact on modern nuclear physics • EFT relates m+d to strong processes like p+d  g + n +n, ann Jiunn-Wei Chen & Peter Kammel

  21. m + d  n + n + nTheory D p MEC EFT  L1A, dR Low Energy Constants • Axial current reaction • Gamow-Teller 3S1 1S0 • one-body currents well defined • FF, deuteron wavefunction, ann • two-body currents not well constrained by theory (short distance physics) • Methods • Potential model + MEC • hybrid EFT (EFT operators, Pot.Model wavefct) • Effective field theories (EFT)

  22. Connection to Neutrino/Astrophysics • Basic solar fusion reaction • p + p  d + e+ +  • Key reactions for Sudbury Neutrino Observatory • e + d  p + p + e- (CC) • x + d  p + n + x (NC) • Intense theoretical studies, scarce direct data • EFT connection to m+d capture via LEC L1A, • Muon capture soft enough to relate to solar reactions with L1A ~ 6 fm3

  23. Quest for L1A, dR “Calibrate the Sun” • Methods • MuSun:by far the best determination in theoretical clean 2-N system hybrid EFT

  24. Precise Experiment Needed consistent ChPT pionless, needs L1A hybrid EFT Potential Model + MEC

  25. μ+d Experiment μ + t + p μd↑↓ μd↑↑ μ + 3He + n dμd μ3He + n complicated, can one extract fundamental weak parameters ? Resonant dmd fusion cycles Lq ~ 10 s-1 Lq ~ 10 s-1 Lq ~ 10 s-1 slow hfs transition μ Ld ~ 400 s-1 Ld ~ 400 s-1 Muon-Catalyzed FusionBreunlich, Kammel, Cohen, LeonAnn. Rev. Nucl. Part. Science, 39: 311-356 (1989) n + n + ν

  26. Optimize Conditions Collisional processes density f dependent Resonant formation rates T dependence Clean interpretation at T = 30 K, f = 5 % of LH2 density md() md md() m3He

  27. Use Basic MuCap Technique • with physics driven changes • New high density cryo-TPC with D2 at 30 K • Extreme purity requirement 1 ppb • Full FADC readout to cope with small signals and copious fusion reactions 100 kV HV gain = 1 Experiment approved PSI PAC 2008

  28. Summary and Outlook gP, EFT • MuCap • First precise gP with clear interpretation • Consistent with ChPT expectation, clarifies long-standing QCD puzzle • Factor 3 additional improvement on the way • MuSun • m+d capture with 10x higher precision • Calibrates basic astrophysics reactions and provides benchmark in axial 2N reactions • Experiment 2008-2011 • Future ProspectsDepending on outcome of current program, RMC, lop ? • New polarization observables ? Synergy with MuLan L1A, EFT, n

  29. V.A. Andreev, T.I. Banks, R.M. Carey, T.A. Case, D. Chitwood, S.M. Clayton, K.M. Crowe, J. Deutsch, J. Egger, S.J. Freedman, V.A. Ganzha, T. Gorringe, J. Govaerts, F.E. Gray, D.W. Hertzog, M. Hildebrandt, P. Kammel, B. Kiburg, S. Knaak, P. Kravtsov, A.G. Krivshich, B. Lauss, E.M. Maev, O.E. Maev, F. Mulhauser, C.S. Özben, C. Petitjean, G.E. Petrov, R. Prieels, G.N. Schapkin, G.G. Semenchuk, M. Soroka, V. Tichenko, A. Vasilyev, A.A. Vorobyov, M. Vznuzdaev, P. Winter http://www.npl.uiuc.edu/exp/mucapture Part of MuCap Petersburg Nuclear Physics Institute (PNPI), Gatchina, RussiaPaul Scherrer Institute (PSI), Villigen, Switzerland University of California, Berkeley (UCB and LBNL), USAUniversity of Illinois at Urbana-Champaign (UIUC), USAUniversité Catholique de Louvain, BelgiumTU München, Garching, GermanyUniversity of Kentucky, Lexington, USABoston University, USA http://www.npl.uiuc.edu/exp/musun supported in part by the United States National Science Foundation, the Department of Energy and the, CRDF, PSI and the Russian Federation and Academy of Sciences

  30. Additional slides

  31. Beyond Standard Model • Additional Physics at Quark-Lepton Level ? • Detailed Chirality Analysis Lincoln Wolfenstein, Ann. Rev. Nucl. Part. Sci. 2003 … The radiative muon capture in hydrogen was carried out only recently with the results that the derived gP was almost 50% too high. If this results is correct, it would be a sign of new physics that might contribute effectively to V, A or P. 0.5 % LS measurement SM except

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