precision muon physics group muon capture on proton - + p + n to 1 % muon capture on proton - +...
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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 experimentgP to < 7% (3%)
muon decay+ e++e+
+ to 1 ppm
muon decay+ e++e+
+ to 1 ppm
Fermi Coupling Constant
Lan experiment
GF 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
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
Quarkhandedness conserved
n
p
-
W
Cap
d
u
-
W
- + p + nelementary level
nucleon level
J = <n| V - Ap>
VgV(q2) + igM(q2)/2M q
AgA(q2) + gP(q2) q/m
J = <n| V - Ap>
VgV(q2) + igM(q2)/2M q
AgA(q2) + gP(q2) q/m
JJ
J = <d| u> J = <d| u>
QCD
pseudoscalar form factor gP
n
p
-
gNN
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 theoryT. Gorringe, H. Fearing, Induced pseudoscalar coupling of the proton weak interaction, nucl-th/0206039, 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
n
d
-
W
n
EFT: Class of axial current reactions related by single unknown parameter L1A
• 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 analogued capture close terrestrial analogue
dp
e
e+W
p• soft enough ?
• precision measurement
possible ?
n
d
-
W
n
D
MEC
EFTL1A
Precision Measurement of Muon Capture on the Proton“Cap experiment”
- + p + n - + p + n
www.npl.uiuc.edu/exp/mucapture/
Petersburg Nuclear Physics Institute (PNPI), Gatchina,RussiaPaul Scherrer Institut, PSI, Villigen, Switzerland
University of California, Berkeley, UCB and LBNL, USAUniversity of Illinois, Urbana-Champaign, USA
Universite Catholique de Louvain, BelgiumTU Munich,Garching, Germany
Boston University, USAUniversity of Kentucky, USA
@ PSICap
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 = 10-3)
• SR effect for +
TS
pp
pp
pp
ortho
para
F=0 F=1
J=1
J=0
n+
n+
n+
Cap
- = heavy electron
Cap experimental strategy I
Cap
New idea: active target of ultra-pure H2 gas 10 bar measure +
and - S = 1/- - 1/+ , to 10-5
New idea: active target of ultra-pure H2 gas 10 bar measure +
and - S = 1/- - 1/+ , to 10-5
eSCe
“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:
1 1
( )' ( )'s
TPC
ePC1
ePC2log(counts)
time
μ+
μ –
1010
events
Cap experimental strategy II
Physics
• Unambigous interpretation At low density (1% LH2) 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 (cZ<10-8, cd<10-6) hydrogen chambers bakeable to 150 C, continuous purification TPC monitors impurities in-situ 10-8 sensitivity with gas chromatograph
• +SR: calibrated with transverse field 70 G
Statistics
• 1010 statistics: Complementary analysis methods Cap
ppP
ppO
p
pp
ppP
ppP
ppO
ppO
time (s)
100% LH2 1 % LH2 10% LH2
Cap experimental setup Key ideas: active target of ultra-pure H2 gas 10 bar for muons, separate large tracking detector for electrons.
Key ideas: active target of ultra-pure H2 gas 10 bar for muons, separate large tracking detector for electrons.
Cap
SC(t = 0)
PC1
PC2
TPC
ePC2ePC1 eSC (Hodoscope)
μ
MuonDetectors
ElectronDetectors 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
Cap status and plans
Planned schedule Cap
• technical proposal spring 2001, received “high priority status”
• commissioning 2003
• final detector upgrades 2004
• data run 2003 4% precision
• data run 2004 1% precision
• …. Cap II or d project
Planned schedule Cap
• technical proposal spring 2001, received “high priority status”
• commissioning 2003
• final detector upgrades 2004
• data run 2003 4% precision
• data run 2004 1% 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 ~ 30-40 MeV/c• rate ~ 50 kHz
LocationPaul Scherrer Institute (PSI),Switzerland