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
APS April 2004 - Denver
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
APS April 2004 - Denver
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)
APS April 2004 - Denver
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.
APS April 2004 - Denver
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)
APS April 2004 - Denver
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
APS April 2004 - Denver
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
APS April 2004 - Denver
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
APS April 2004 - Denver
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 !
APS April 2004 - Denver
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
APS April 2004 - Denver
F=1/2
d d
F=3/2
n n
D Q
hf
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 = 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 !!!
APS April 2004 - Denver
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
APS April 2004 - Denver
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
APS April 2004 - Denver
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
APS April 2004 - Denver
Setup Setup Stage 2Stage 2-Neutron -Neutron TOFTOF
nnnn
xy
TPC
entrancecounter
deuterium gascooled with liquid N2
with enough physics motivation
APS April 2004 - Denver
Thanksfor your attention !
APS April 2004 - Denver
APS April 2004 - Denver
APS April 2004 - Denver
F=1/2
d d
F=3/2
n n
D Q
APS April 2004 - Denver
F=1/2
d d
F=3/2
n n
D Q
hfdd CF
nhf populationmonitoring
3Hecapture background !
recycling
APS April 2004 - Denver
F=1/2
d d
F=3/2
n n
D Q
hf
APS April 2004 - Denver
dd
APS April 2004 - Denver
CF
nhf populationmonitoring
3Hecapture background !
recycling
APS April 2004 - Denver
dd CF
nhf populationmonitoring
3Hecapture background !
recycling