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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 U C B e r k e l e y for the MuCAP Collaboration Petersburg Nuclear Physics Institute Paul Scherrer Institut University of California - Berkeley and LBNL
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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 U C B e r k e l e y for the MuCAP Collaboration Petersburg Nuclear Physics Institute Paul Scherrer Institut University of California - Berkeley and LBNL University of Illinois - Urbana Champaign Universite Catholique de Louvain Boston University University of Kentucky - Lexington Universität München The muD-Project - experiment under consideration - encourage strongly community input APS April 2004 - Denver
m 2 hyperfine states: (1/2) md (3/2) md doublet capture rate: Ld 1/2 ~ 400s-1 quartet capture rate: Ld 3/2 ~ 10s-1 md md n n d F=1/2 F=3/2 LD W LQ m- nm n n nm The Basic Process to be investigated is muon capture on the deuterium doublet state m + d n + n + n APS April 2004 - Denver
Why a new experiment on md-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 APS April 2004 - Denver
The Present Experimental Situation is unsatisfying lifetime measurement F= 5%; ultraclean D2 gas n-measurement F=4% gas, T=40K 409±40 lifetime measurement liquid D2, T=18K 470±29 n-measurement H2-D2(5%) gas mixture, T=293K but only if pure 1/2 population assumed / statistical mix -> x3 n-measurement liquid H2-D2(0.32%) mixture T=18K Problems: n-method: depends on n-efficiency and energy threshold -> needs theory for extraction of L. lifetime method: needs high statistics & target purity. APS April 2004 - Denver
New Calculation Ando et al. PLB 533 (2002) EFT* (HBCPT+EFT) reduces MECs effect |1B|2 = 370 s-1 |1+2B|2 = 386 s-1 Test of the Standard Nuclear Physics Approach and of Meson Exchange Currents SNPA 2-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 (p,r exchange / significant D-isobar current) MECs are sensitive to short range effects enhanced for high energetic neutrons ann- final state interaction gp dependence (similar to mp-capture) SNPA Tatara et al PRC42(1990) MECs 10% of total rate APS April 2004 - Denver
Theory The Present Experimental Situation is controvers lifetime measurement F= 5%; ultraclean D2 gas n-measurement F=4% gas, T=40K 409±40 lifetime measurement liquid D2, T=18K 470±29 Theory cannot account for rates at 470 s-1 ! ! ! n-measurement H2-D2(5%) gas mixture, T=293K but only if pure 1/2 population assumed / statistical mix -> x3 n-measurement liquid H2-D2(0.32%) mixture T=18K Problems: n-method: depends on n-efficiency and energy threshold -> needs theory for extraction of L. lifetime method: needs high statistics & target purity. APS April 2004 - Denver
EFT(p) 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 known a NLO calculation contains one not so well determined parameter denoted L1,A or dR - Ld 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 ) ^ APS April 2004 - Denver Test of calculational approach via Effective Field Theory
Astrophysical Interest because of the close connection between muon capture and neutrino 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 b-decay - n d &n d scattering & breakup reactions -> SNO L1,A can be determined from: _ 3-body current ? assumes standard 8B shape no solar model uncertainties included (fB,12 ,dm212constraint) _ suggested md capture ? ± 1.5 fm3 Chen-Kammel would be the most precise determination from 2-body system APS April 2004 - Denver
Knowledge of L1,A is important for a precision determination of neutrino parameters 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) L1,A necessary to determine absolute rates in SNO ! constrain 13 ! APS April 2004 - Denver
Due to the complexity of muonic processes in deuterium it is very important for a precision measurement to determine the most favourable experimental conditions. APS April 2004 - Denver
recycling m mCF Lhf md md dmd F=1/2 F=3/2 LD LQ n n n m3He hf population monitoring nm capture background ! Muons are subject to a Complex Chain of Processes in Deuterium APS April 2004 - Denver
F = 0.01 LHD T = 300K F = 0.1 LHD T = 300K Well known Variation of the Muonic Deuterium Hyperfine Populations with Temperature and Density — 1/2 states— 3/2 states— sum 1/2+3/2 — dd-fusion neutron APS April 2004 - Denver
F = 0.01 LHD T = 80K F = 0.1 LHD T = 80K Well known Variation of the Muonic Deuterium Hyperfine Populations with Temperature and Density liquid N2 - cooling possible !!! — 1/2 states— 3/2 states— sum 1/2+3/2 — dd-fusion neutron APS April 2004 - Denver
MuCAP Experience with precision Lifetime Measurement in Hydrogen 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) APS April 2004 - Denver
Setup Stage 1 - Lifetime Measurement ( MuCAP ) X X e-detectors mu-detectors cooled TPC D2 gas system measure at 300 K to 3% precision with present setup APS April 2004 - Denver
EFT* little contribution to L because of small overlap of wavefunctions of the deuteron and the 2 neutrons n pEFT pEFT ? n final state interaction nn-scattering length Investigation of Energy Dependence - Dalitz Plot m + d n + n + n APS April 2004 - Denver
deuterium gas cooled with liquid N2 with enough physics motivation Setup Stage 2 -Neutron TOF APS April 2004 - Denver
Thanks for your attention ! APS April 2004 - Denver
m md md F=1/2 F=3/2 LD LQ n n nm APS April 2004 - Denver
recycling m mCF Lhf md md dmd F=1/2 F=3/2 LD LQ n n n m3He hf population monitoring nm capture background ! APS April 2004 - Denver
m Lhf md md F=1/2 F=3/2 LD LQ n n nm APS April 2004 - Denver
dmd APS April 2004 - Denver
recycling mCF n m3He hf population monitoring capture background ! APS April 2004 - Denver
recycling mCF dmd n m3He hf population monitoring capture background ! APS April 2004 - Denver