Muon Capture on the Deuteron Motivation for a new Experiment B e r n h a r d L a u s s

Muon Capture on the DeuteronMuon Capture on the DeuteronMotivation for a new ExperimentMotivation for a new Experiment

B e r n h a r d L a u s s B e r n h a r d L a u s s U C B e r k e l e yU C B e r k e l e y

for thefor the

MuCAP CollaborationMuCAP CollaborationPetersburg Nuclear Physics InstitutePetersburg Nuclear Physics Institute

Paul Scherrer Institut Paul Scherrer Institut University of California - Berkeley and LBNLUniversity of California - Berkeley and LBNL

University of Illinois - Urbana ChampaignUniversity of Illinois - Urbana ChampaignUniversite Catholique de LouvainUniversite Catholique de Louvain

Boston UniversityBoston UniversityUniversity of Kentucky - LexingtonUniversity of Kentucky - Lexington

Universität MünchenUniversität München

APS April 2004 - Denver

The muD-Project

- experiment under consideration

- encourage strongly community input


The Basic Process to be The Basic Process to be investigated is muon capture on investigated is muon capture on

the deuterium doublet statethe deuterium doublet state

+ d n + n +

d nn

-

W

hyperfine states: (1/2) d (3/2) d

doublet capture rate: d 1/2 ~ 400s-1

quartet capture rate: d 3/2 ~ 10s-1F=1/2

d d

F=3/2

n n

D Q


Why a new experiment on Why a new experiment on d-d-capture ?capture ?

» First precise Measurement of charge current reaction in a 2 Nucleon system

» Test of 2-body currents (Axial) Meson Exchange Currents

» Resolve unclear experimental situation

» Determine L1,A -> relevant for Neutrino experiments & Solar Model

200 300 400 500 600

projectedprecision 1%

1989 Vienna

1986 Saclay

1970 Cern

1965 Columbia

d capture rate d(s-1)


The Present Experimental Situation is The Present Experimental Situation is unsatisfyingunsatisfying

n-measurement=4% gas, T=40K

lifetime measurementliquid D2, T=18K

n-measurementH2-D2(5%) gas mixture, T=293K but only if pure 1/2 population assumed / statistical mix -> x3

n-measurementliquid H2-D2(0.32%) mixtureT=18K

lifetime measurement= 5%; ultraclean D2 gas

409±40

470±29

Problems: n-method: depends on n-efficiency and energy threshold -> needs theory for extraction of . lifetime method: needs high statistics & target purity.


SNPA2-body nuclear system is well known test of our description of nuclear response to weak probes at intermediate energies; two nucleon interaction. test of MECs ( exchange / significant isobar current)MECs are sensitive to short range effectsenhanced for high energetic neutrons ann - final state interaction gp dependence (similar to p-capture)

Test of the Standard Nuclear Physics Test of the Standard Nuclear Physics Approach and of Meson Exchange Approach and of Meson Exchange

CurrentsCurrentsSNPA Tatara et al PRC42(1990)MECs 10% of total rate

New CalculationAndo et al. PLB 533 (2002) EFT* (HBCPT+EFT)reduces MECs effect

|1B|2 = 370 s-1

|1+2B|2 = 386 s-1

200 300 400 500 600

projectedprecision 1%

1989 Vienna

1986 Saclay

1970 Cern

1965 Columbia

d capture rate d(s-1)


The Present Experimental Situation The Present Experimental Situation is controversis controvers

n-measurement=4% gas, T=40K

lifetime measurementliquid D2, T=18K

n-measurementH2-D2(5%) gas mixture, T=293K but only if pure 1/2 population assumed / statistical mix -> x3

n-measurementliquid H2-D2(0.32%) mixtureT=18K

lifetime measurement= 5%; ultraclean D2 gas

409±40

470±29

Problems: n-method: depends on n-efficiency and energy threshold -> needs theory for extraction of . lifetime method: needs high statistics & target purity.

TheoTheoryry

Theory cannot account for rates at 470 s-

1 ! ! !

Test of calculational approach Test of calculational approach via Effective Field Theoryvia Effective Field Theory


EFT( EFT*

- uses a low-energy expansion scheme with a set cut-off parameter for regularization

- provides independent framework with model-independent results when all low-energy coefficients in the effective Lagrangian are knowna NLO calculation contains one not so well determined parameter denoted L1,A or dR

d can be used to determine precisely the low-energy parameter within a 2-body system(Ando-Park-Kubodera-Myhrer PLB533(2002)25 / Kammel-nucl-ex/0304019 )

^

Astrophysical Interest because of the close Astrophysical Interest because of the close connection between muon capture and connection between muon capture and

neutrino scattering calculationneutrino scattering calculation


EFT: Class of axial current reactions related by one single low-energy parameter L1,A (Butler-Chen-Kong PRC63 (2001)035501)

- pp-fusion- tritium -decay- d &d scattering & breakup reactions -> SNO

L1,A can be determined from:tritium -decay 4.2 ± 0.1 fm3 Schiavilla / Butler (3-body)reactor -d 3.6 ± 4.6 fm3 Butler-Chen-Vogeldimensional analysis 6 ± 6 fm3 Butler-Chen-KongSNO & SuperK 4.0 ± 6.3 fm3 Chen-Heeger-RobertsonHelioseismology 4.8 ± 5.9 fm3 Brown-Butler-GuentherSNO 4.5 ± 3.0 fm3 Balantekin-YukselORLaND ??????????? ?????????????

_

_ 3-body current ?

assumes standard 8B shape no solar model uncertainties included (fB,12 ,m21

2 constraint)

suggested d capture ? ± 1.5 fm3 Chen-Kammel would be the most precise determination from 2-body system


The leading two-body current parametrized by L1,A is the dominant uncertainty of every low-energy weak interaction deuteron breakup process including SNO’s CC and NC reactions ! (Chen-Heeger-Robertson PRC67-2003 )We emphasize the importance of fixing the axial counter term through a direct experimental measurement ! (Butler-Chen-Kong/PRC63-2001)

Knowledge of LKnowledge of L1,A1,A is important for a is important for a precision determination of neutrino precision determination of neutrino

parametersparameters

constrain 13 !L 1,A

necessary to

determine absolute

rates in SNO !


Due to the Due to the complexity of muonic complexity of muonic

processesprocessesin deuteriumin deuterium

it is very important it is very important for a precision measurementfor a precision measurement

to determine to determine the most favourable the most favourable

experimental conditions.experimental conditions.

CF

nhf populationmonitoring

3Hecapture background !

recycling

dd

Muons are subject to a Muons are subject to a Complex Chain of Complex Chain of Processes in DeuteriumProcesses in Deuterium


F=1/2

d d

F=3/2

n n

D Q

hf


Well known Variation of the Muonic Well known Variation of the Muonic Deuterium Hyperfine Populations with Deuterium Hyperfine Populations with Temperature and DensityTemperature and Density

= 0.01 LHDT = 300K

= 0.1 LHDT = 300K

— 1/2 states — 3/2 states — sum 1/2+3/2— dd-fusion neutron

— 1/2 states — 3/2 states — sum 1/2+3/2— dd-fusion neutron APS April 2004 - Denver

Well known Variation of the Muonic Well known Variation of the Muonic Deuterium Hyperfine Populations with Deuterium Hyperfine Populations with Temperature and DensityTemperature and Density

= 0.01 LHDT = 80K

= 0.1 LHDT = 80K

liquid N2 - cooling possible !!!


Comparison Hydrogen / Deuterium Experiments

in D2 easier - isotopic purity requirements less stringent

in D2 harder- muonic molecular processes- additional neutron measurement - control of hyperfine states- cooled TPC detector with higher density (smaller chamber)

MuCAP MuCAP Experience with precision Lifetime Experience with precision Lifetime

Measurement in HydrogenMeasurement in Hydrogen


Setup Stage 1Setup Stage 1- Lifetime - Lifetime MeasurementMeasurement( MuCAP )( MuCAP )

e-detectors mu-detectors cooled TPC D2 gas system

XX

measure at 300 K to 3% precisionwith present setup

Investigation of Energy Dependence - Investigation of Energy Dependence - Dalitz PlotDalitz Plot


final state interactionnn-scattering length

little contribution to because of small overlap of wavefunctions of the deuteron and the 2 neutrons

EFT

EFT ?

+ d n + n +

n

n

EFT*

close neutronarray

charged particleveto counters

Active target: TPCinside D2 pressure vessel

far neutronarray

charged particleveto counters

-b

eam

xy

start counter


Setup Setup Stage 2Stage 2-Neutron -Neutron TOFTOF

nnnn

xy

TPC

entrancecounter

deuterium gascooled with liquid N2

with enough physics motivation


Thanksfor your attention !




F=1/2

d d

F=3/2

n n

D Q


F=1/2

d d

F=3/2

n n

D Q

hfdd CF



recycling


F=1/2

d d

F=3/2

n n

D Q

hf


dd


CF



recycling


dd CF



recycling

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Muon Capture on the Deuteron Motivation for a new Experiment B e r n h a r d L a u s s