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Tests of symmetries with nuclei (in nuclear b decay)

Tests of symmetries with nuclei (in nuclear b decay). Oscar Naviliat-Cuncic LPC-Caen, ( ENSI–CNRS/IN2P3) and Université de Caen Basse-Normandie Caen, France. Goal and Outline. Review achievements of precision measurements in nuclear beta decay aiming to test fundamental symmetries.

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Tests of symmetries with nuclei (in nuclear b decay)

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  1. Tests of symmetries with nuclei(in nuclear b decay) Oscar Naviliat-Cuncic LPC-Caen, (ENSI–CNRS/IN2P3)and Université de Caen Basse-Normandie Caen, France

  2. Goal and Outline • Review achievements of precision measurements in nuclear beta decay aiming to test fundamental symmetries. • Present (selected) ongoing projects. (Biased choice) 1. General context 2. Tests of Maximal parity violation 3. Tests of Time Reversal Invariance 4. Searches for other exotic interactions 5. Summary

  3. Context and motivations • evidence for “new physics” is expected to manifest itself either at the high energy frontier (direct production of new particles) or at the high precision frontier (search for tiny effects). • effects have to be looked for everywhere where improvements in experimental sensitivities are possible (atoms, nuclei, particles) (unless strong theoretical counter arguments) • consider here experiments in nuclear beta decay (including neutron)

  4. Beta decay correlations Jn Pp e pe p • What we imagine to occur • (at the quark-lepton level) 1. Integrate over all vectors: decay rates or lifetimes 2. Integrate/average over all spin vectors: angular correlation 3. Integrate some spins and momenta: pseudo-scalar correlations • What we have access to • (experimentalist toolbox) 4. Integrate (less) spins and momenta: triple correlations a, A, G, D, Rcontain the dynamics and probe the symmetries

  5. 1. Parity violation P space inversion r→ -r axial vector J→J (invariant) polar vector p→-p (changes sign) • P is assumed to be maximally violated in the SM • Searching for deviations probe new physics (like RHC) • Look at pseudo-scalar quantities Terms in the decay rate distribution that change sign under parity ( J · p )"decay asymmetry" ( s· p )"longitudinal polarization" …Enhanced sensitivity if one combines both of them

  6. Polarization-Asymmetry correlation J q b nuclear spin beta polarimeter “Beta particles from polarized nuclei should be polarized” H.A. Tolhoek and S.R. DeGroot Physica17 (1951) 1 Absolute b longitudinal polarization from polarized nuclei (within V-A) • A asymmetry parameter • J degree of nuclear polarization • q angle between J and pe Perform relative measurement at different emission angles …and look for deviations from SM

  7. Measurement in 12N decay reaction chamber spectrometer polarimeter B b+ Stack Target MgO powder stop 10 cm TDCstart (LLN, ETH-Zurich, Wisconsin, Leuven) Injector1@PSI • production: • polarization analysis: time resolved spectroscopy of hf Ps decay [E. Thomas et al., NP 694 (2001) 559] Results Can be considered as the most precise tests of maximal parity violation in nuclear beta decay (in terms of constraints on RHC)

  8. (Slow) progress on constraints: global fits Maximal parity violation implies C’V = CV Boothroyd, Markey, Vogel, 1984 PRC 29 (1984) 603 Severijns, Beck, Naviliat-Cuncic, 2006 RMP 78 (2006) 991 96-(61+13)+34 = 56 data values 69-1+28 = 96 data values

  9. Neutrino asymmetry: K MOT at TRIUMF J pv D.Melconian, J.Behr & Co Top view Side view • Not competitive yet with present constraints. • Setup has been upgraded: new beta detectors, larger chamber,… • New data expected soon. • Pioneering work on 38mK atom trapping • Measured the bn angular correlation in 38mK • Extended setup to polarize 37K • Detect recoiling ions in coïncidence Bn = -0.755(24) [D.Melconian et al., PLB 649 (2007) 370]

  10. 2. Time reversal invariance axial vector J→ -J (changes sign) polar vector p→-p (changes sign) T Time reversal t → -t • T violation = CP violation • In processes involving the lightest quarks, the CKM CP violating effect is strongly suppressed (out of experimental reach) • Large window for new physics (provided FSI effects are accounted for) P-even, T-odd correlation: P-odd, T-odd correlation: (mixed) (GT and mixed) Do not probe the same physics

  11. R in a mixed transition : neutron at PSI 50 cm Pb-foil Pb-foil scintillator scintillator MWPC (Cracow, PSI, Caen, Leuven, Katowice) lead by Prof. K.Bodek & Co Maximum sensitivity for mutually perpendicular vectors • Polarized cold neutrons (SINQ@PSI) • Transverse polarization analysis by Mott scattering on Pb-foil • Tracking of electrons in low-mass, low-Z MWPC • Identification of Mott events by vertex • Frequent neutron spin flipping and foil IN/OUT

  12. R in a mixed transition : neutron at PSI • Analysis in terms of geometric form factors averaged over the setup geometry Vertex identification Example of data sample Pb-foil Rexp = 0.008(16) Nexp = 0.056(12) RSM = 0.0006(2)NSM = 0.068(1) [A. Kozela at al., PRL 102 (2009) 172301] • Already obsolete (additionally analyzed data will improve precision by a factor 2) • Determines also the N coefficient (electron polarization along neutron spin) to check polarimetry

  13. R in a GT : 8Li at TRIUMF (Rikkyo, KEK, TRIUMF), J.Murata & Co. • Goal: improve by a factor 20 the best measurement so far in a GT transition [R. Huber et al., PRL 90 (2003) 202301] (reach the FSI level). • 8Li source ~107 pps – 80% pol. @ 30keV • Implanted in annealed Pt at room temp.; B=500G • Apparatus installed at TRIMF • Test beam run planned in Nov.2010

  14. 3. Exotic couplings • bn angular correlation (even under P and T transformations) • within the SM x : Fermi fraction; r : GT/F mixing ratio • beyond the SM a contains quadratic S and T contributions …detect the recoiling ion to deduce neutrino momentum

  15. a in GT : 6He Paul trap @ GANIL LPCTrap@GANIL RFQ cooler buncher URF hat ring “ideal” 3D Paul trap First transparent prototype Fully transparent trap (rings)

  16. LPCTrap results TOF neutrino mass • GOAL: Measure the bn angular correlation in 6He decay with (Da/a)stat < 0.5% • First data taking run in 2006 [X. Fléchard et al., PRL101 (2008) 212504] All position sensitive detectors; complete kinematics • (2008): collected 4×106 (for stat) and 2×106 (for sys studies) events. • Statistical precision reached; data analysis under way.

  17. a in Fermi : WITCH Penning trap @ ISOLDE First recoil ion spectrum 124Sn recoils Retardation potential (V) (K.U.Leuven, Uni. Munster, ISOLDE, GSI, NPI Rez-Prague) N.Severijns et al. • Goal: measure bn correlation in 35Ar with (a/a)stat  0.5 % • Detect recoiling ions in singles • Select ion energies sequentially: retardation potential [V.Yu. Kozlov et al., NIM B 266 (2008) 4515] • Too low 35Ar production/transport so far • System being upgraded

  18. Summary • Precision measurements in nuclear beta decay have made significant progress over the past decade. (progress is slow) • Dozens of new projects using radioactive nuclei, cold neutron beams and UCNs are under way (patience needed) • New results are expected soon, in particular from experiments with atom and ion traps. Thanks to: K.Bodek, D.Melconian, J.Murata, N.Severijns, for inputs

  19. Constraints on Scalar couplings [J.C. Hardy and I.S. Towner, PRC 79 (2009) 055502]

  20. Constraints on Tensor couplings A in 114In

  21. Constraints on sums of exotic couplings

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