Precision Muon Physics Group muon capture on proton  - + p   + n  to 1 % muon capture on proton  - + p   + n  to 1 % Nucleon form factors, chiral symmetry of QCD  Cap experiment g P to < 7% (3%) muon decay  +  e + + e +    + to 1 ppm muon decay  +  e + + e +    + to 1 ppm Fermi Coupling Constant  Lan experiment G F to < 1ppm muon capture on deuteron  - + d   + n +n  to 1 % muon capture on deuteron  - + d   + n +n  to 1 % Basic EW two nucleon reaction, calibrate v-d reactions  D project K.D. Chitwood, P. Debevec, S. Clayton, D. Hertzog, P. Kammel, B. Kiburg, R. McNabb, F. Mulhauser, C. C. Polly, A. Sharp, D. Webber

Scientific case  Cap QCD is the theory of strong interactions non Abelian Gauge theory, running coupling constant, Precision tests at high energies strong coupling, confinement at “everyday” energies Theoretical approaches to low energy domain QCD inspired models Lattice QCD Effective field theories (chiral perturbation theory) systematic expansion around chiral limit “spontaneous broken” symmetry governs dynamics mass generation accurate QCD prediction and QCD foundation for models model independent predictions of important reactions Quark handedness conserved

n  p -- W  Cap d  u -- W  - + p   + n elementary level nucleon level J  = V   g V (q 2 )   + ig M (q 2 )/2M   q  A   g A (q 2 )     + g P (q 2 ) q  /m   JJ JJ J  = QCD pseudoscalar form factor g P n  p --  g  NN FF W fundamental and least known weak nucleon FF solid theoretical prediction at 2-3% level basic test of QCD symmetries experiments not precise, controversial, 4  discrepancy to theory T. Gorringe, H. Fearing, Induced pseudoscalar coupling of the proton weak interaction, nucl-th/ , Jun 2002 V. Bernard et al., Axial Structure of the Nucleon, Nucl. Part. Phys. 28 (2002), R1

 D project  + d  n + n + fundamental EW 2-body reaction high impact for fundamental astrophysics reactions 10x precision improvement feasible by  Cap techniques fundamental EW 2-body reaction high impact for fundamental astrophysics reactions 10x precision improvement feasible by  Cap techniques DD n  d -- W n

 EFT: Class of axial current reactions related by single unknown parameter L 1A basic solar fusion reaction p + p  d + e + + key reactions for solar neutrino detection and supernova neutrino + d  p + p + e + d  p + n + short distance, axial two body currents, ab-inito  EFT (NNLO) vs. SNPA vs. MEEFT  d capture close terrestrial analogue d p e e+e+ W p soft enough ? precision measurement possible ? n  d -- W n DD MEC EFT L 1A

Precision Measurement of Muon Capture on the Proton “  Cap experiment”  - + p   + n Petersburg Nuclear Physics Institute (PNPI), Gatchina,Russia Paul Scherrer Institut, PSI, Villigen, Switzerland University of California, Berkeley, UCB and LBNL, USA University of Illinois, Urbana-Champaign, USA Universite Catholique de Louvain, Belgium TU Munich,Garching, Germany Boston University, USA University of Kentucky, PSI  Cap

experimental challenges    e+ e +   - p (  )   + n p (Rich) physics effects Interpretation: where does capture occur ? Critical because of strong spin dependence of V-A interaction Background: Wall stops and diffusion Transfer to impurities  p+Z   Z +p Rate and statistics (BR = )  SR effect for  + TT SS  pp  pp pp  ortho  para F=0 F=1 J=1 J=0 n+  Cap  - = heavy electron

 Cap experimental strategy I  Cap New idea: active target of ultra-pure H 2 gas 10 bar measure   + and   -   S = 1/   - - 1/   +,   to eSC e “Lifetime” or “Disappearance” Method Our experiment observes e + and e – decay products. Muon capture reduces the μ – lifetime compared to the μ + lifetime by 0.15% ! High precision measurement of the lifetime difference: TPC ePC1 ePC2 log(counts) time μ+μ+ μ – events

 Cap experimental strategy II 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 (c Z <10 -8, c d <10 -6 ) hydrogen chambers bakeable to 150 C, continuous purification TPC monitors impurities in-situ sensitivity with gas chromatograph  + SR: calibrated with transverse field 70 G Statistics statistics: Complementary analysis methods  Cap 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

 Cap experimental setup Key ideas: active target of ultra-pure H 2 gas 10 bar for muons, separate large tracking detector for electrons.  Cap  SC (t = 0)  PC1  PC2 TPC ePC2 ePC1eSC (Hodoscope) μ Muon Detectors Electron Detectors e

 Cap experimental setup: TPC The time projection chamber (TPC), is our active gas-filled target. It detects in muons and reaction products in 3D.  stop rare impurity capture  +Z  Z’+n+

2003 run  Cap Assembly: March → August Data-Taking: September → mid-October. commissioning / first physics

time spectra 2003

 Cap status and plans Planned schedule  Cap technical proposal spring 2001, received “high priority status” commissioning 2003 final detector upgrades 2004 data run % precision data run % precision ….  Cap II or  d project  Cap Steve’s and Tom’s thesis Contact me if you are interested !

Experimental facility Muon Source PSI accelerator (ring cyclotron) generates 590 MeV proton beam protons hit graphite target and produce pions pions decay to muons Muon Beam Properties Particles: μ + or μ – Momentum ~ MeV/c rate ~ 50 kHz Location Paul Scherrer Institute (PSI), Switzerland