muon capture @ psi peter winter university of washington gpgp l 1a / d r

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)


• Current statusCurrent status

dd

pp

-

p n

- + p n +

M ~ GFVud · (1-5) · n(V-A)p

q2 = -0.88m2

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


• 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

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








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 facility: The facility: E3 beamline at PSIE3 beamline at PSI

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

Lifetime spectraLifetime spectra

NormalizedNormalizedresiduals residuals

OutlineOutline








dd

pp

Internal corrections to Internal corrections to --

(statistical uncertainty of -: 13.7 s-1)

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

Internal corrections to Internal corrections to --

(statistical uncertainty of -: 13.7 s-1)

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








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








dd

pp

d kineticsd kinetics

μ

μd↑↑

μd↑↓

dμd

μZD

n + n +

μ3He + n

μ + 3He + n

μ + t + p

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)

muon capture @ psi peter winter university of washington gpgp l 1a / d r

Documents

saclaym p n n g

resultsmuon capture

poutlinemuon capture

cdoutlinemuon capture

proton mucap motivation

deuteron musun motivation

axial current

pure h22