Muon Capture in Hydrogen and Deuterium EXA 08

Muon Capture in Hydrogen and Deuterium EXA 08 int. conference on exotic atoms & related topics Vienna Sept 15 -18 2008 presentation by Claude Petitjean representing the Mu. Cap- & the Mu. Sun collaboration g. P vs. λop plot showing first Mu. Cap result collaboration homepages http: //www. npl. uiuc. edu/exp/mucapture http: //www. npl. uiuc. edu/exp/musun

outline - experimental goals - comments to theories Ch. PT g. P - EFT L 1 A - experimental challenges & strategy - - μ kinetics in hydrogen - the ortho-para problem - Mu. Cap apparatus, components - data & 1 st results, final analysis - Mu. Sun experiment: the new challenges - μd-kinetics - new Cryo-TPC - outlook

Muon Capture Experiments in Hydrogen & Deuterium our goal precision measurement of muon capture rates to ± 1% 1) μ- + p → (μ-p)↑↓ → n + νμ singlet capture rate ΛS sensitive to induced pseudoscalar coupling g. P in weak interactions first results published – full analysis in progress 2) μ- + d → (μ-d)↑↓ → n + νμ doublet capture rate ΛD sensitive to the axial two-body current term L 1 A in effective field theories (EFT‘s) in full preparation – first run in Nov 2008

scientific case of μ capture on the proton μ capture probes axial structure of nucleon μ capture neutron β decay μ- + p ν μ + n n p μ- W n (analogue) p W νμ eνe hadronic vertex determined by QCD: q 2 dep. form-factors (g. V, g. M, g. A, g. P) μp-capture is the only process sensitive to the nucleon form factor gp heavy baryon chiral perturbation theory (Bernard et al. 1994): g. Ptheory = 8. 26 0. 23 - gp least known of the nucleons weak form factors - solid theoretical prediction by HBCh. PT at 2 -3% level - basic test of QCD symmetries

scientific case of μ capture on the deuteron μ + d n + νμ model-independent connection via EFT & L 1 A • • impact on fundamental astrophysics processes (SNO, pp) basic solar fusion reaction p + p d + e+ + key reactions for SNO + d p + e- (CC) + d p + n + (NC) comparison of modern high precision calculations (eff. field theories, standard nucl. physics approach) EFT: axial current reactions related by single parameter L 1 A • the muon capture rate on deuteron determines L 1 A MEC EFT L 1 A

- only n & ν in output channel limited precision for direct measurement of absolute rates use lifetime method ΛS = λ(μ-p) – λ(μ+) measure λ‘s to 10 ppm >~ 1010 events required - capture rate small ~ 10 -3 of λ(μ+) avoid any wall stops to 10 -5! develop ultra-clean TPC as active muon stop target operated in hydrogen gas log(counts) experimental challenges & our strategy (I) m → e λ + λ - LS reduces lifetime by 10 -3 μ+ μ– te-tm

experimental challenges & our strategy (II) - μ-transfer to impuries (N 2, H 2 O, . . ) μp + N (O, . . ) → μN (μO, . . ) + p distortion of lifetime curves develop continuously circulating & cleaning system (CHUPS) goal: c. Z ~ 10 -8 (10 ppb) - μ-transfer to deuterium μp + d → μd + p & large diffusion of μd atoms distortion of lifetime curves develop new special isotope separation column goal: cd < 10 -7 (100 ppb)

experimental challenges & our strategy (III) kinetics of μ- in H 2 n+n ΛT ~ 12 s-1 pμ↑↑ μ- τ~10 ns triplet (F=1) Λppμ n+n ΛOM ~540 s-1 ppμ ortho (J=1) pμ↑↓ singlet (F=0) ΛS~710 s-1 - n+n λOP ΛPM ~213 s-1 ppμ para (J=0) pμ↑↑ depopulates quickly (<100 ns) - ppμ molecule formation with (τ ~ 0. 4μs/φ) Λppμ known only to ± 20% - ortho to para transition rate badly known λOP known only to ± 50% n+ - ΛS - ΛOM - ΛPM are all quite different! solution: - use low gas density φ (10 bar H 2) ≈ 1% of liquid - determine Λppμ by Argon doped run – λOP from neutron spectra

CAD view of Mu. Cap experimental setup e

the 10 bar Hydrogen TPC wires on glass frames - pure metallic & ceramic structures bakeable to 130 C ultra-pure protium gas el. drift field 2 k. V/cm vdrift = 0. 5 cm/μs UHV = 30 k. V Ucath = 5 -6 k. V MWPC readout in x-z bottom planes sensitive volume (12 x 15 x 30) cm 3

high gas purity maintained by continuous circulation - operated by cryogenic adsorption/desorption cycles in active Carbon - traps all higher Z impurities by Zeolites immersed in liquid Nitrogen our main impurity is water vapor outgasing from walls & materials

control & calibrations of impurities event display showing impurity capture event humidity of TPC protium was monitored with PURA device ~17 ppb reached 35 strips H 2 O 75 anode wires test admixing of 21 ppm N 2: cleaned off to <10 ppb N 2 time axis (60 μs)

HD separation column constructed in Gatchina & PSI, tested & operated in March/April 2006 principle: - H 2 gas circulates from bottom to top & gets liquified at the cold head - liquid droplets fall down & evaporize gas phase depleted from D - the D-enriched liquid H 2 at the bottom is slowly removed results of AMD analysis at ETHZ: protium in 2004/5: cd = (1. 45± 0. 15)10 -6 protium used in 2006 after HD separation: cd < 6*10 -9 (6 ppb)

final 2004 lifetime fit (1. 6*109 good μ- events) chosen impact cut 120 mm ( small μd correction!) λμ- = 455‘ 851. 4 ± 12. 5 stat ± 8. 5 syst s-1 (main Mu. Cap result) λμ+ = 455‘ 162. 2 ± 4. 4 s-1 (new world average incl. μLAN) 455’ 164 ± 28 (Mu. Cap result with 0. 6*109 μ+ events) μ- lifetime curves 2004 data resulting μp capture rate: ΛS = 725. 0 17. 4 s-1 theory (+ radiative corr. ): ΛS = 710. 6 3 s-1

g. P vs λOP plot with first unambiguous Mu. CAP result our result is g. P = 7. 3± 1. 1 (HBCh. PT: 8. 26± 0. 23) g. P TRIUMF SACLAY λop

final Mu. Cap analysis data 2004 statistics result / errors: stat. 1. 6 * 109 (published) syst. total ΛS = 725. 0 ± 13. 7 ± 10. 7 ± 17. 4 s-1 (2. 4%) g. P = ± 1. 1 (15%) 7. 3 2005 -07 1. 8 * 1010 expect δΛS to ± 3. 7 (analysis in progress) ± 4 ± 5. 5 s-1 (0. 8%) δg. P to ± 0. 35 (5%) (HBCh. PT: 8. 26± 0. 23) ************** list of systematic errors [s-1]: topic 2004 2005 -07 method of improvement Z>1 impurities 5. 2 2 improved CHUPS-system, FADC μd diffusion 1. 6 <0. 1 isotope separator (cd < 6 ppb) analysis methods 6. 6 3 improved analysis programs, MC ppμ form. rate (Λppμ) 5 0. 5 measurement (Argon doped run) ortho-para rate (λOP) 3. 5 2 measurement of neutron spectra ----------------------------sum of syst. errors 10. 7 s-1 4 s-1 completion of final analysis in 2009

Argon doped run for Λppμ measurement - protium run with 20 ppm Argon doping electron spectrum 5. 5*108 events neutrons from μAr capture 3*105 events tpc data from μ-Ar capture 4*106 evts combined analysis of time spectra yields λcapt. Ar , λtransferp. Ar , λppμ to ~2% reduces error of ΛS to 0. 5 s-1 ! (analysis in progress at Urbana) e- time spectrum yields λe neutron time spectrum Ar capture time spectrum

authors of first μp capture results published in Phys. Rev. Letters 99, 032002 (2007) V. A. Andreev, T. I. Banks, T. A. Case, D. Chitwood, S. M. Clayton, K. M. Crowe, J. Deutsch, J. Egger, S. J. Freedman, V. A. Ganzha, T. Gorringe, F. E. Gray, D. W. Hertzog, M. Hildebrandt, P. Kammel, B. Kiburg, S. Knaak, P. Kravtsov, A. G. Krivshich, B. Lauss, K. L. Lynch, E. M. Maev, O. E. Maev, F. Mulhauser, C. S. Özben, C. Petitjean, G. E. Petrov, R. Prieels, G. N. Schapkin, G. G. Semenchuk, M. Soroka, V. Tichenko, A. Vasilyev, A. A. Vorobyov, M. Vznuzdaev, P. Winter Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia Paul Scherrer Institute (PSI), Villigen, Switzerland University of California, Berkeley (UCB and LBNL), USA (graduate students in red) University of Illinois at Urbana-Champaign (UIUC), USA Université Catholique de Louvain, Belgium University of Kentucky, Lexington, USA Boston University, USA parts of the collaboration during the main run in 2006 at PSI

the Mu. Sun experiment nuclear muon capture on the deuteron there are new challenges compared to μp capture: - at room temperature the μd spin state is badly known due to slow spin flip rate and strong ddμ formation + fusion (see kinetics) - transfer rates to impurities are significantly larger technical solution: go to low temperatures (~30 K) And higher gas density (5 -10% of liquid, up from 1%) Λ(μd 3/2 μd 1/2) ~ 3 x 106 s-1 impurities (H 2 O, etc) freeze out

μd kinetics slow spin flip and resonant dμd fusion cycles μd↑↑ μ μ dμd μ + 3 He + n μd↑↓ ΛD + t + p μZ n + ν

effect of ddμ kinetics md( ) 1% LD 2 300 K md( ) at low density φ=1%, 300 K (as μp capture experiment): - spin flip very slow - rate not precisely known (± 15%) no precise interpretation of observed capture rate possible m 3 He time ( s) 30 K, LD 2 10% 30 5%K at higher density (φ=5 -10%), 30 K (proposed for μd capture experiment): - strong depopulation of quartet state - observable in dμd fusion time spectrum pure μd(F=1/2) state capture rate highest (~400 s-1) conclusion: develop cryo-tpc for μd experiment

setup of Mu. Sun detector e e. SC e. PC 2 e. PC 1 m. PC Cryo-TPC m. SC m

technical design of the cryo-system liquid Neon cooling circuit (vibration free) continuous cleaning by CHUPS

CAD view of cryo tpc, vacuum & cooling system

outlook - Nov 2008 first test run using still the Mu. Cap setup (300 K) 10 bar high purity deuterium charge collection on 8 x 10 cm 2 pad plane studies of: - impurity events, controls, cleaning ddμ fusion events measure μ transfer rate to impurities neutron spectra - fall 2009 commissioning run with new cryo tpc at 30 K - 2010 -11 main statistics runs ~2*1010 events