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Peter Kammel

First Results from the New Muon Lifetime Experiments at PSI. G F. g P. Peter Kammel. MuLan. MuCap. L 1A. “MuSun” project. MuCap. g P. MuCap Physics Case. EW current key probe Understanding hadrons from QCD Symmetries of Standard Model Muon Capture Formfactors.

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Peter Kammel

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  1. First Results from the New Muon Lifetime Experiments at PSI GF gP Peter Kammel MuLan MuCap L1A “MuSun”project

  2. MuCap gP MuCap Physics Case • EW current key probe • Understanding hadrons from QCD • Symmetries of Standard Model • Muon Capture • Formfactors • - + p  m+ n rateLSat q2= -0.88 mm2 The Black Sheep of Form Factors T. Hemmert + second class currentssuppressed by isospin symm. Lorentz, T invariance All form factors precisely known fromSM symmetries and data apart from gP = 8.3 ± 50%

  3. MuCap gpNN n p p Fp W m- nm Pseudoscalar Form Factor gP gP determined by chiral symmetry of QCD: gP= (8.74  0.23) – (0.48  0.02) = 8.26  0.23 PCAC pole term Adler, Dothan, Wolfenstein ChPT leading order one loop two-loop <1%N. Kaiser Phys. Rev. C67 (2003) 027002 • gP basic and experimentally least known EW nucleon form factor • solid QCD prediction via HBChPT (2-3% level) • basic test of QCD symmetries Recent reviews:T. Gorringe, H. Fearing, Rev. Mod. Physics 76 (2004) 31V. Bernard et al., Nucl. Part. Phys. 28 (2002), R1

  4. MuCap 1 % LH2 100% LH2 pm ppμ ppmO ppμ pm ppmO ppmP ppmP time (ms) Interpretationof Experiments ? LT = 12 s-1 triplet (F=1) pμ↑↑ Lortho=506s-1 Lpara=200s-1 λop μ ppμ ppμ f λppm ortho (J=1) para (J=0) pμ↑↓ • Interpretation requires knowledge of ppm population • Strong dependence on hydrogen density f singlet (F=0) LS= 710s-1 n+n

  5. MuCap MuCap Experimental Strategy • Lifetime method • 1010m→enn decays • measure - to 10ppm, • S = 1/- - 1/+to 1% • Unambiguous interpretation at 1% LH2 density • Clean m stop definition in active target (TPC) to avoid wall stops • Ultra-pure gas system and purity monitoring at 10 ppb level • Isotopically pure “protium” m → enn LSreduces lifetime by 10-3 • + log(counts) • - μ+ μ – te-tm fulfill all requirements simultaneouslyunique MuCap capabilities

  6. 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

  7. MuCap 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

  8. MuCap Results arXiv:0704.2072v1 [nucl-ex] accepted PRL SMuCap = 725.0  13.7stat 10.7sys s-1 further sub percent theory required Average of HBChPT calculations of S: Apply new rad. correction (2.8%): arXiv:0704.3968v1 [hep-ph]Czarnecki, Marciano,Sirlin gP = 7.3 ± 1.1 (MuCap 2007)

  9. MuCap gP Landscape after MuCap 06 • - + p  m + n + g Before MuCap experiments inconclusive and mutually inconsistent MuCap • MuCap result nearly model independent First precise and unambiguous result • Consistent with chiral prediction Does not confirm radiative muon capture (RMC) discrepancy • Final result (’06 and ’07 data) will reduce error twofold

  10. MuLan MuLan Scientific Case • Fundamental electroweak parameters • GF • Implicit to all EW precision physics • Uniquely related to muon decay • PrecisionGF t relation no longer theory limited • GFaMZ 9 ppm 0.0007 ppm 23 ppm QED exp MuLan2004 theory 17 ppm 18 ppm 90 ppb 30 ppm9 ppm 18 ppm <0.3 ppm0.5 ppm 1 ppm <0.3 ppm van Ritbergen and Stuart: 2-loop QED corrections MuLan Goal

  11. MuLan MuLan Experiment Real data Kicker On “Early-to-late” changes • Instrumental shifts Gain or threshold Time response • Effective acceptance Residual polarization or precession Pileup • Missing events PSI DC proton beam590 MeV, 1.7 mA Systematics Measurement Period Number (log scale) time Fill Period -12.5 kV 12.5 kV

  12. MuLan 6/5/07 accepted PRL arXiv:0704.1981v1 [hep-ex] tm(MuLan) = 2.197 013(21)(11) ms (11ppm) tm(World) = 2.197 019(21) ms (9.6 ppm) GF = 1.166 371(6) x 10-5 GeV-2(5 ppm)

  13. MECEFT L1A m + d  n + n + n “Calibrating the Sun” via Muon Capture on the Deuteron “MuSun” proposal end 2007 model-independent connection via EFT & L1A • Goal • total md capture rate to 1% precision • Motivation • first precise measurement of basic EW reaction in 2N system, benchmark measurement with 10x higher precision • impact on fundamental astrophysics reactions (SNO, pp) • comparison of modern high precision calculations (EFT/SNPA) • high precision feasible by mCap technique and careful optimization

  14. Synergy and Outlook • MuLan • MuCap 20 ppm10 ppm1 ppm ??30 ppm10 ppm log(counts) 2008 projected 2006 μ+ μ – time • MuSun needs both, gP and precision lifetimes

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