Precision Muon Physics mX

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Precision Muon Physics - mX
MuCAP MuLAN
Bernhard Lauss University of California _at_
Berkeley
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Precision Measurement of the Positive Muon
Lifetime Muon Lifetime Analysis
µ lifetime
MuLAN
Courtesy D. Hertzog
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Basics
µ lifetime 2.19703 ms
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MuLAN Goals Requirements
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MuLAN concept / subsystems
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m
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LEDs
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170
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µSR Muon Spin Rotation
Helmholz coils supply a 70-gauss, transverse (x-y
plane) magnetic field over the target volume.
Decay es are preferentially emitted in the
direction of the µ spin. Residual polarization
effects will produce direction-dependent
distortions in the µ lifetime histograms.
µ beam, spins partially polarized along z-axis
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First Test-Data
Courtesy D. Chitwood
(136 ppm)
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MuLAN Schedule
Run Plan Summer 2003 - Setup and Test of
final beam line with kicker - Setup and test of
DAQ - Finalize Detectors and Electronics
(WFDs) - Detector Comissioning Run 2004 -
Obtain full statistics
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MuLAN Collaborating Institutions MuCap
Petersburg Nuclear Physics Institute (PNPI),
Gatchina, RussiaPaul Scherrer Institute (PSI),
Villigen, Switzerland University of California,
Berkeley (UCB and LBNL), USAUniversity of
Illinois, Urbana-Champaign (UIUC), USAUniversite
Catholique de Louvain, BelgiumTU Muenchen,
Garching, GermanyUniversity of Kentucky,
Lexington, USABoston University, USAJames
Madison University, USA Ls 3 Ls 3
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Precision Measurement of the Singlet Muon Capture
Rate on the Proton
µ- capture on hydrogen
MuCAP
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Basics
µ lifetime 2.19703 ms
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Weak-Interaction V-A, gV, gA
involving Hadrons -gt more complex
-gt 6 Formfactors
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Nucleon charged current at q2 - 0.88 mm2
Ja Va - Aa Va gV(q2) ga igM(q2)/2M sab
qb gS(q2)/m qa Aa gA(q2) ga g5 gP(q2)
qa/m g5 igT(q2)/2M sab qb g5
Capture Rate
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pseudoscalar form factor gP
PCAC gP8.7
gpNN
n
p
p
Fp
heavy baryon chiral perturbation theory
m-
nm
gP(8.74 ? 0.23) (0.48 ? 0.02) 8.26 ? 0.23
gpNN 13.31(34) 13.0(1)13.05(8)
L calculations O(p3) show good convergence 100
25 3
delta effect small
LO NLO NNLO
fundamental and least known weak nucleon FF
solid theoretical prediction at 2-3 levelbasic
test of QCD symmetries Recent reviewsT.
Gorringe, H. Fearing, Induced pseudoscalar
coupling of the proton weak interaction,
nucl-th/0206039, Jun 2002V. Bernard et al.,
Axial Structure of the Nucleon, Nucl. Part. Phys.
28 (2002), R1
NLO result
Courtesy P.Kammel
mCap
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Experimental Status gP and muon capture -
unsatisfying
update from Gorringe Fearing
RMC
gP
ChPT
mCap proposed
OMC Saclay
exp
theory
lOP (ms-1)
RMC 4s discrepancy exp/th No overlap
between OMC not precise, ambiguous
interpretation theory/RMC/OMC
!
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µ Kinetics in Hydrogen -gt Experimental Challenges
strong spin dependence of V-A
interaction Background Wall stops and
diffusion Transfer to impurities mpZ ? mZ p
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experimental strategy
Experimental Challenges / Solutions

• Physics
• Unambigous interpretation At low density (1
  LH2) mostly capture from mp(F0) atomic
  state.
• Clean muon stop definition Wall stops and
  diffusion eliminated by 3-D muon tracking
• In situ gas impurity control (cZlt10-8, cdlt10-6)
  hydrogen chambers bakeable to 150 C,
  continuous purification TPC monitors capture on
  impurity and transfer to deuterium 10-8
  sensitivity with gas chromatograph
• mSR calibrated with tranverse field 70 G

100 LH2
1 LH2
10 LH2
pm
pm
ppmO
ppmO
pm
ppmO
ppmP
ppmP
ppmP
time (ms)

• Statistics
• 1010 statistics Complementary analysis methods
  

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Experimental idea active target of ultra-pure
H2 gas 10 bar measure t?
and t?- ? ?S 1/??- - 1/?? , tm to 10-5
mCap experimental strategy
Hodoscope
ePC2
ePC1
µ BEAM
Pressure Vessel for TPC (10 bar deuterium
depleted protium)
e
eSC
Detectors cover 75 of 4p µ,e detectors are
decoupled to prevent cross-talk
mCap
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Experimental Setup TPC
The time projection chamber (TPC) operates in
proportional mode (gain 104)
field shaping wires
- bakeable - quartz glass with very low thermal
expansion
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TPC features
- track reconstruction - pileup protection -
vertex matching between muon and decay electron -
determination of low levels of Zgt1 impurities in
the H2 gas
Sensitivity is 0.01 ppm
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m transfer to deuterium, diffusion, mCF
mpd ? md p
Diffusion
Ramsauer Townsend minimum in md p scattering
at 1.6 eV Check by comparing m and m-
m-catalyzed pd fusion (Alvarez)
md p ? pmd ? m(5.3MeV)3He(0.2KeV)
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time projection chamber
mCap e-detector
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Observed µSR
opposite counters
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MuCap Timetable
Summer 2003 Finalize detector integration and
full speed DAQ
Fall 2003 First attempt at accumulating full
1010 statistics. Ls 3
2004 Further statistics recording as needed
Muons on request beam -gt Ls 3
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Summary
Nucleon form factors, chiral symmetry of QCD m
Cap experimentgP to lt 7 (3 with mLan kicker)
muon capture on proton ?- p ? ?m n L to 1
Fermi Coupling Constant m Lan experiment GF to lt
1ppm
muon decay? ? ene?m t? to 1 ppm
Future
Basic EW two nucleon reaction, calibrate v-d
reactions L1a mD project
muon capture on deuteron ?- d ? ?m n n L
to 1
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MuCAT
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