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 APS April Denver The muD-Project - experiment under consideration - encourage strongly community input
APS April Denver The Basic Process to be investigated is muon capture on the deuterium doublet state + d n + n + d nnnn -- W hyperfine states: (1/2) d (3/2) d doublet capture rate: d 1/2 ~ 400s -1 quartet capture rate: d 3/2 ~ 10s -1 F=1/2 dd dd F=3/2 n n DD QQ
APS April Denver Why a new experiment on d-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 L 1,A -> relevant for Neutrino experiments & Solar Model
APS April Denver The Present Experimental Situation is unsatisfying n-measurement =4% gas, T=40K lifetime measurement liquid D2, T=18K 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 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 Denver 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 ( exchange / significant isobar current) MECs are sensitive to short range effects enhanced for high energetic neutrons a nn - final state interaction g p dependence (similar to p- capture) Test of the Standard Nuclear Physics Approach and of Meson Exchange Currents SNPA Tatara et al PRC42(1990) MECs 10% of total rate 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
APS April Denver The Present Experimental Situation is controvers n-measurement =4% gas, T=40K lifetime measurement liquid D2, T=18K 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 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.Theory Theory cannot account for rates at 470 s -1 ! ! !
Test of calculational approach via Effective Field Theory APS April 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 known a NLO calculation contains one not so well determined parameter denoted L 1,A or d R 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/ ) ^
Astrophysical Interest because of the close connection between muon capture and neutrino scattering calculation APS April Denver EFT: Class of axial current reactions related by one single low-energy parameter L 1,A ( Butler-Chen-Kong PRC63 (2001) ) - pp-fusion - tritium -decay - d & d scattering & breakup reactions -> SNO L 1,A can be determined from: _ _ 3-body current ? assumes standard 8B shape no solar model uncertainties included (f B, 12, m 21 2 constraint) suggested d capture ? ± 1.5 fm 3 Chen-Kammel would be the most precise determination from 2-body system
APS April Denver The leading two-body current parametrized by L 1,A is the dominant uncertainty of every low-energy weak interaction deuteron breakup process including SNO’s CC and NC reactions ! ( Chen-Heeger-Robertson PRC ) We emphasize the importance of fixing the axial counter term through a direct experimental measurement ! ( Butler-Chen-Kong/PRC ) Knowledge of L 1,A is important for a precision determination of neutrino parameters constrain 13 ! L 1,A necessary to determine absolute rates in SNO !
APS April 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.
CF n hf population monitoring 3 He capture background ! recycling dddd Muons are subject to a Complex Chain of Processes in Deuterium APS April Denver F=1/2 dd dd F=3/2 n n DD QQ hf
APS April Denver Well known Variation of the Muonic Deuterium Hyperfine Populations with Temperature and Density = 0.01 LHD T = 300K = 0.1 LHD T = 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 Denver Well known Variation of the Muonic Deuterium Hyperfine Populations with Temperature and Density = 0.01 LHD T = 80K = 0.1 LHD T = 80K liquid N2 - cooling possible !!!
APS April Denver Comparison Hydrogen / Deuterium Experiments in D 2 easier - isotopic purity requirements less stringent in D 2 harder - muonic molecular processes - additional neutron measurement - control of hyperfine states - cooled TPC detector with higher density (smaller chamber) MuCAP Experience with precision Lifetime Measurement in Hydrogen
APS April Denver Setup Stage 1 - Lifetime Measurement ( MuCAP ) e-detectors mu-detectors cooled TPC D2 gas system XXXX measure at 300 K to 3% precision with present setup
Investigation of Energy Dependence - Dalitz Plot APS April Denver final state interaction nn-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*
APS April Denver Setup Stage 2 -Neutron TOF deuterium gas cooled with liquid N2 with enough physics motivation
APS April Denver Thanks for your attention !
APS April Denver
F=1/2 dd dd F=3/2 n n DD QQ
APS April Denver F=1/2 dd dd F=3/2 n n DD QQ hf dddd CF n hf population monitoring 3 He capture background ! recycling
APS April Denver F=1/2 dd dd F=3/2 n n DD QQ hf
APS April Denver dddd
CF n hf population monitoring 3 He capture background ! recycling
APS April Denver dddd CF n hf population monitoring 3 He capture background ! recycling