Muon capture @ PSIMuon capture @ PSI
Peter WinterPeter Winter
University of WashingtonUniversity of Washington
gP
L1A / dR
OutlineOutline
Muon capture on the proton (MuCap)Muon capture on the proton (MuCap)
• Motivation and general overviewMotivation and general overview
• MuCap experimentMuCap experiment
• Systematics and resultsSystematics and results
Muon capture on the deuteron (MuSun)Muon capture on the deuteron (MuSun)
• Motivation and general overviewMotivation and general overview
• Current statusCurrent status
dd
pp
OutlineOutline
Muon capture on the proton (MuCap)Muon capture on the proton (MuCap)
• Motivation and general overviewMotivation and general overview
• MuCap experimentMuCap experiment
• Systematics and resultsSystematics and results
Muon capture on the deuteron (MuSun)Muon capture on the deuteron (MuSun)
• Motivation and general overviewMotivation and general overview
• Current statusCurrent status
dd
pp
Nucleon form factorsNucleon form factors
Conserved Vector Current and isospin symmetryConserved Vector Current and isospin symmetry ggSS(q(q22) = 0) = 0
ggVV, g, gMM: strong program JLab, Mainz, ...: strong program JLab, Mainz, ...
V = gV(q2)
+ i gM(q2) q/2MN
+ gS(q2) q/m
M ~ GFVud · (1-5) · n(V-A)p
Second class current suppressed by isospin Second class current suppressed by isospin g gTT(q(q22) = 0) = 0
ggAA(q(q22) measured in neutron decay) measured in neutron decay
A = gA(q2) 5
+ i gT(q2) q/2MN5
+ gP(q2) q/m5
M ~ GFVud · (1-5) · n(V-A)p
Nucleon form factorsNucleon form factors
• solid QCD prediction via ChPT (2-3% level)solid QCD prediction via ChPT (2-3% level)
• NNLO < 1%: NNLO < 1%: N. Kaiser, PRC67 (2003)N. Kaiser, PRC67 (2003)
• basic test of chiral symmetries and low energy QCDbasic test of chiral symmetries and low energy QCDRecent 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 gPP
gP(q2) = - - gA(0)mNmrA2
2mNm¹gA(0)
q2-m¼2
1
3gP(q2) = -
2mNmgA(0)
q2-m2
PCAC pole termPCAC pole term(Adler, Dothan, Wolfenstein)(Adler, Dothan, Wolfenstein)
NLO (ChPT)NLO (ChPT)Bernard, Kaiser, MeissnerBernard, Kaiser, Meissner
PR D50, 6899 (1994)PR D50, 6899 (1994)
ggPP = 8.26 ± 0.23 = 8.26 ± 0.23
p n
W
gNN
f
How to access gHow to access gPP??
In principle any process directly involving axial current:In principle any process directly involving axial current:
- - decay: Not sensitive since g decay: Not sensitive since gPP term ~ q term ~ q
- - scattering difficult to measure scattering difficult to measure
Muon capture most direct source for gMuon capture most direct source for gPP
Experiments: Observed ProcessesExperiments: Observed Processes
- Ordinary muon capture (OMC): - Ordinary muon capture (OMC): - - p p nn
- Radiative muon capture (RMC): - Radiative muon capture (RMC): - - p p nn
- - - 3- 3He He 33H or other nucleiH or other nuclei
Experiments: Observed ProcessesExperiments: Observed Processes
- Ordinary muon capture (OMC): - Ordinary muon capture (OMC): - - p p nn
- Radiative muon capture (RMC): - Radiative muon capture (RMC): - - p p nn
- - - 3- 3He He 33H or other nucleiH or other nuclei
OMC: Methods to measureOMC: Methods to measure
Neutron experiments:Neutron experiments:- Measure outgoing neutrons N- Measure outgoing neutrons NNN
- Requires knowledge of neutron efficiency- Requires knowledge of neutron efficiency
- Separation of decay - Separation of decay 's from neutrons's from neutrons- Typical experiments 8-13% precision in - Typical experiments 8-13% precision in SS
Lifetime method:Lifetime method:- - SS 1/ 1/-- - 1/ - 1/++
Hydrogen density, (LHHydrogen density, (LH22: : =1)=1)
Muon kineticsMuon kinetics
μ
pμ↑↑
pμ↑↓
p
T ~ 12s-1
S ~ 700s-1
>0.01<100ns
Muon kineticsMuon kinetics
pμ↑↓
S ~ 700s-1
OP
ortho (J=1)
ppμOF
para (J=0)
ppμ
PF
OM ~ ¾ S
PM ~ ¼ S
• pppp formation depends on density formation depends on density • Interpretation requires knowledge of Interpretation requires knowledge of OMOM, , PMPM and and OPOP
= 1 (Liquid)= 1 (Liquid)
Rel
. P
op
ula
tio
n
Time after p Formation
= 0.01 (~10 bar gas)= 0.01 (~10 bar gas)
Time after p Formation
Rel
. P
op
ula
tio
n
pμ↑↓
S ~ 700s-1
OP
ortho (J=1)
ppμOF
para (J=0)
ppμ
PF
OM ~ ¾ S
PM ~ ¼ S
Previous resultsPrevious results
20 40 60 80 100 120
2.5
5
7.5
10
12.5
15
17.5
20
ChPT
OP (ms-1)
Cap precision goal
exp theory TRIUMF 2005
p n @ SACLAY
p n @ TRIUMFgP
• no overlap theory, OMC & RMCno overlap theory, OMC & RMC• large uncertainty in large uncertainty in OPOP g gPP ± 50% ± 50%
Requirement of clean targetRequirement of clean target
pμ↑↓
S ~ 700s-1
OP
ortho (J=1)
ppμOF
para (J=0)
ppμ
PF
OM ~ ¾ S
PM ~ ¼ S
Isotopically and chemically pure HIsotopically and chemically pure H22, ideally:, ideally:
ccdd<1 ppm, c<1 ppm, cZZ<10 ppb<10 ppb
μd
ccddpd
μZ
ccZZZ
d
Z ~ S Z4
diffusion
OutlineOutline
Muon capture on the proton (MuCap)Muon capture on the proton (MuCap)
• Motivation and general overviewMotivation and general overview
• MuCap experimentMuCap experiment
• Systematics and resultsSystematics and results
Muon capture on the deuteron (MuSun)Muon capture on the deuteron (MuSun)
• Motivation and general overviewMotivation and general overview
• Current statusCurrent status
dd
pp
MuCap in a nutshellMuCap in a nutshell
• Lifetime method:Lifetime method:101010 10 decays decays SS to 1% precision to 1% precision
• Low gas density Low gas density Capture mostly from F=0 Capture mostly from F=0
• Active gas target (TPC) Active gas target (TPC) Clean Clean stop stop
• Ultra pure gas system with in-situ monitoringUltra pure gas system with in-situ monitoringccZZ ~ 10 - 30 ppb (Z = N ~ 10 - 30 ppb (Z = N22, H, H22O)O)
• Isotopically pure hydrogen gasIsotopically pure hydrogen gasccdd ~ 100 ppb (deuterium separation) ~ 100 ppb (deuterium separation)
The KickerThe Kicker
Kicker
• Design at TRIUMFDesign at TRIUMF
• MOSFET basedMOSFET based
• 50 ns switching time50 ns switching time
Other elementsOther elements
Quadrupoles
Detector
Separator
Separator: Separator: Suppression ofSuppression ofee++ or e or e-- in beam in beam
TPC - the active targetTPC - the active target
• 10 bar ultra-pure H10 bar ultra-pure H22
• 2.0 kV/cm drift field 2.0 kV/cm drift field
• ~ 5.4 kV on 3.5 mm ~ 5.4 kV on 3.5 mm anode half gapanode half gap
• bakeable bakeable glass/ceramic glass/ceramic materialsmaterials
Operation with pure HOperation with pure H22 challenging, R&D @ PNPI, PSI challenging, R&D @ PNPI, PSI
TPC - the active targetTPC - the active target
p
E
e-
-
entrance: lower energy loss stop: Bragg peak
• 3d tracking without material in fiducial volume• Clean muon stop definition away from high-Z
y
x
z
xz projectionfrom anodes and strips
zy projectionfrom anodes and drift time
xy projectionfrom strips and drift time
OutlineOutline
Muon capture on the proton (MuCap)Muon capture on the proton (MuCap)
• Motivation and general overviewMotivation and general overview
• MuCap experimentMuCap experiment
• Systematics and resultsSystematics and results
Muon capture on the deuteron (MuSun)Muon capture on the deuteron (MuSun)
• Motivation and general overviewMotivation and general overview
• Current statusCurrent status
dd
pp
CHUPSCHUPS
ccN2N2, c, cO2O2 < 10 ppb < 10 ppb
CContinous ontinous HH22 UUltra-ltra-PPurification urification SSystemystem
NIM A578 (2007), 485NIM A578 (2007), 485
Impurity monitoring Impurity monitoring
2004 run: 2004 run: ccNN < 7 ppb, c < 7 ppb, cH2OH2O~30 ppb~30 ppb
2006 / 2007 runs: 2006 / 2007 runs: ccNN < 7 ppb, c < 7 ppb, cH2OH2O~10 ppb~10 ppb
Imp. Capture: Z (Z-1) n
MuCap's unique capabilityMuCap's unique capability
World Record: cd < 100 ppb
On site purification since 2006On site purification since 2006• MuCap 2004 data:MuCap 2004 data:
ccdd = 1.49 = 1.49 ±± 0.12 ppm 0.12 ppm
• AMS, ETH ZurichAMS, ETH Zurichccdd = 1.44 = 1.44 ±± 0.15 ppm 0.15 ppm
Precise and unambiguous MuCap resultPrecise and unambiguous MuCap result
V.A. Andreev et al., Phys. Rev. Lett. 99, 03202 (2007)
Using new MuLan average
Recent muon capture review: P. Kammel and K. Kubodera, Ann. Rev. Nucl. Part. Sci., Vol 60 (2010)
ggPP evaluation evaluation
Final analysis (10Final analysis (101010 muon decays) muon decays)
50% of final statistics
• Many hardware upgrades (readout, purification, kicker)
• 10x higher statistics
• Analysis far advanced (many subtle effects studied)
• Unblinding expected in first half of 2011
OutlineOutline
Muon capture on the proton (MuCap)Muon capture on the proton (MuCap)
• Motivation and general overviewMotivation and general overview
• MuCap experimentMuCap experiment
• Systematics and resultsSystematics and results
Muon capture on the deuteron (MuSun)Muon capture on the deuteron (MuSun)
• Motivation and general overviewMotivation and general overview
• Current statusCurrent status
dd
pp
MuSun: "Calibrating" the sunMuSun: "Calibrating" the sun
+ d + d n + n + n + n +
model-independent connection via EFT & Lmodel-independent connection via EFT & L1A1A
Aim: Measure rate Aim: Measure rate dd from from d(d() to < 1.5 %) to < 1.5 %
TheoryTheory
• One body currents well definedOne body currents well defined
• Two body currents not well Two body currents not well constrained by theory (short dist.)constrained by theory (short dist.)
• Methods:Methods: Potential model + MECPotential model + MEC less or hybrid EFT (Lless or hybrid EFT (L1A1A / d / dRR))
• Muon capture soft enough to Muon capture soft enough to relate to solar reactionsrelate to solar reactions
MEC
EFT
L1A, dR
Precise experiment neededPrecise experiment needed
Potential Model + MEC
pionless, needs L1A
hybrid EFT
consistent ChPT
OutlineOutline
Muon capture on the proton (MuCap)Muon capture on the proton (MuCap)
• Motivation and general overviewMotivation and general overview
• MuCap experimentMuCap experiment
• Systematics and resultsSystematics and results
Muon capture on the deuteron (MuSun)Muon capture on the deuteron (MuSun)
• Motivation and general overviewMotivation and general overview
• Current statusCurrent status
dd
pp
d()
d()
d
He
Optimized conditionsOptimized conditions
Clean interpretation at:Clean interpretation at:
T = 30 K, T = 30 K, = 5% LH = 5% LH22 density density
Cryo-TPC developmentCryo-TPC developmentCold headCold head
Neon condensorNeon condensor
Neon heatNeon heatpipepipe
Vibration-freeVibration-freesupportsupport
Cryo-TPCCryo-TPC
Vacuum Vacuum vesselvessel
Cryo-TPC developmentCryo-TPC developmentAluminum
shell
Rear neon collector
Front neon collector
Be window flange Be window
500 Mhzwaveformdigitization
Come by and take a sunny tour....Come by and take a sunny tour....
Current status:Current status:
• T = 30 KT = 30 K
• HV = 80 kVHV = 80 kV
• Purity excellentPurity excellent
• Improved resolution of TPCImproved resolution of TPC
Overall summaryOverall summary
MuCap:– First precise gP with clear interpretation
– Consistent with ChPT expectation, clarifies long-standing puzzle
– Factor 3 additional improvement on the way (unblinding in first half of 2011)
MuSun– Muon-deuteron capture with 10x
higher precision– Calibrates basic astrophysics reactions and
provides new benchmark in axial 2N reactions
Recent muon capture review: P. Kammel and K. Kubodera, Ann. Rev. Nucl. Part. Sci., Vol 60 (2010)