peter kammel
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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Peter Kammel
First Results from the New Muon First Results from the New Muon Lifetime Experiments at PSILifetime Experiments at PSI
GFgP
L1A
MuCap
“MuSun”project
MuLan
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EW current key probe Understanding hadrons from QCD Symmetries of Standard Model
Muon Capture
Formfactors
MuCap Physics CaseMuCap Physics Case
MuCap
- + p + n rateS at q2= -0.88 m2- + p + n rateS at q2= -0.88 m
2
Lorentz, T invariance+ second class currentssuppressed by isospin symm.
apart from gP = 8.3 ± 50% apart from gP = 8.3 ± 50%
All form factors precisely known fromSM symmetries and data
gg
PP
The Black Sheep of Form Factors T. Hemmert
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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
• 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
Pseudoscalar Form Factor gPseudoscalar Form Factor gPPMuCa
p
n
p
-
gNN
F
W
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InterpretationInterpretation of Experiments ?of Experiments ?
T = 12 s-1
pμ↑↓
singlet (F=0)
S= 710 s-1
n+
triplet(F=1)
μ
pμ↑↑
ppμ
para (J=0)ortho (J=1)
λop
ortho=506 s-1 para=200 s-1
ppμ ppμ ppμ
• Interpretation requires knowledge of pp population
• Strong dependence on hydrogen density
ppP
ppO
p
100% LH2
p
ppP
ppO
1 % LH2
time (s)
λ pp
MuCap
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Lifetime method
1010 →e decays
measure to 10ppm,
S = 1/ - 1/to 1%
Unambiguous interpretation at 1% LH2 density Clean stop definition in active target (TPC) to avoid wall stops
Ultra-pure gas system and purity monitoring at 10 ppb level
Isotopically pure “protium”
MuCap Experimental StrategyMuCap Experimental Strategy
fulfill all requirements simultaneouslyunique MuCap capabilities
MuCap
log
(co
un
ts)
te-t
μ+
μ –
S reduces lifetime by 10-3
→ e
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3D tracking w/o material in fiducial volume
Muons stop in active TPC targetMuons stop in active TPC target
p-
Observed muon stopping distribution
E
e-
10 bar ultra-pure hydrogen, 1.16% LH2
2.0 kV/cm drift field ~5.4 kV on 3.5 mm anode half gapbakeable glass/ceramic materials
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Time SpectraTime Spectra
-e impact parameter cut
huge background suppression
diffusion (deuterium) monitoring
blinded master clock frequency
variety of consistency checks
6 m
m In
sid
e T
PC
MuCap
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ResultsResults
SMuCap = 725.0 13.7stat 10.7sys s-1S
MuCap = 725.0 13.7stat 10.7sys s-1
Average of HBChPT calculations of S:
(MuCap 2007)gP = 7.3 ± 1.1gP = 7.3 ± 1.1
Apply new rad. correction (2.8%):
arXiv:0704.2072v1 [nucl-ex]
arXiv:0704.3968v1 [hep-ph]Czarnecki, Marciano,Sirlin
further sub percent theory required
MuCap
accepted PRL
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• 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
• 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
ggP P Landscape after MuCap 06Landscape after MuCap 06
Before MuCap experiments inconclusive and mutually inconsistent
MuCap
MuCap
- + p + n +
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MuLan Scientific CaseMuLan Scientific Case
Fundamental electroweak parameters
GF
Implicit to all EW precision physics
Uniquely related to muon decay
PrecisionGF relation no longer theory limited
9 ppm 0.0007 ppm 23 ppm
GF MZ
QED
MuLan2004
MuLanGoal
theory 17 ppm 18 ppm 90 ppb 30 ppm 9 ppm 18 ppm <0.3 ppm
0.5 ppm 1 ppm <0.3 ppm
17 ppm 18 ppm 90 ppb 30 ppm 9 ppm 18 ppm <0.3 ppm
0.5 ppm 1 ppm <0.3 ppm
van Ritbergen and Stuart:
2-loop QED corrections
MuLan
exp
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PSI DC proton beam590 MeV, 1.7 mA
Kicker On
Fill Period
Measurement Period
time
Num
ber
(log
scal
e)
-12.5 kV
12.5 kV
Real data
MuLan ExperimentMuLan Experiment“Early-to-late” changes
• Instrumental shiftsGain or threshold
Time response
• Effective acceptanceResidual polarization or precession
Pileup
• Missing events
Systematics
MuLan
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MuLan = 2.197 013(21)(11) s (11ppm)
(World) = 2.197 019(21) s (9.6 ppm)
GF = 1.166 371(6) x 10-5 GeV-2 (5 ppm)
MuLan = 2.197 013(21)(11) s (11ppm)
(World) = 2.197 019(21) s (9.6 ppm)
GF = 1.166 371(6) x 10-5 GeV-2 (5 ppm)
arXiv:0704.1981v1 [hep-ex]
MuLan
6/5/07 accepted PRL
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“Calibrating the Sun” via Muon Capture on the Deuteron + d + d n + n + n + n +
Goal
total d 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 Cap technique and careful optimization
model-independent connection via EFT & Lmodel-independent connection via EFT & L1A1A
MEC
EFTL1A
proposal end 2007
“MuSun”
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Synergy and OutlookSynergy and Outlook
log
(co
un
ts)
timeμ+
μ –
20 ppm 10 ppm 1 ppm?? 30 ppm 10 ppm
2006 2008projected
•MuLan
•MuCap
•MuSun needs both, gP and precision lifetimes