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**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

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**Goal and Outline 1. General context**

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 MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**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) MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Beta decay correlations**

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) e pe Pp Jn p 4. Integrate (less) spins and momenta: triple correlations a, A, G, D, R contain the dynamics and probe the symmetries MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**P 1. Parity violation P is assumed to be maximally violated in the SM**

Searching for deviations probe new physics (like RHC) Look at pseudo-scalar quantities P space inversion r → -r axial vector J → J (invariant) polar vector p → -p (changes sign) 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 MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Polarization-Asymmetry correlation**

“Beta particles from polarized nuclei should be polarized” H.A. Tolhoek and S.R. DeGroot Physica 17 (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 J beta polarimeter b nuclear spin q …and look for deviations from SM MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Measurement in 12N decay b+ Decay (R-1)x104 Lab. 107In 740±410 LLN '93**

Stack Target reaction chamber 10 cm TDC start stop spectrometer polarimeter b+ B MgO powder (LLN, ETH-Zurich, Wisconsin, Leuven) production: polarization analysis: time resolved spectroscopy of hf Ps decay [E. Thomas et al., NP 694 (2001) 559] Results Decay (R-1)x104 Lab. 107In 740±410 LLN '93 12N 6±34 PSI '01 Can be considered as the most precise tests of maximal parity violation in nuclear beta decay (in terms of constraints on RHC) MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**(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 data values 96-(61+13)+34 = 56 data values MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Neutrino asymmetry: K MOT at TRIUMF**

D.Melconian, J.Behr & Co Top view Side view J pv 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 = (24) [D.Melconian et al., PLB 649 (2007) 370] MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**2. Time reversal invariance**

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) T Time reversal t → -t axial vector J → -J (changes sign) polar vector p → -p (changes sign) P-even, T-odd correlation: P-odd, T-odd correlation: (mixed) (GT and mixed) Do not probe the same physics MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**R in a mixed transition : neutron at PSI**

(Cracow, PSI, Caen, Leuven, Katowice) lead by Prof. K.Bodek & Co Maximum sensitivity for mutually perpendicular vectors Polarized cold neutrons Transverse polarization analysis by Mott scattering on Pb-foil MWPC scintillator Pb-foil 50 cm Tracking of electrons in low-mass, low-Z MWPC Identification of Mott events by vertex Frequent neutron spin flipping and foil IN/OUT MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**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 = (2) NSM = 0.068(1) [A. Kozela at al., PRL 102 (2009) ] 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 MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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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) ] (reach the FSI level). 8Li source ~107 pps – 80% 30keV Implanted in annealed Pt at room temp.; B=500G Apparatus installed at TRIMF Test beam run planned in Nov.2010 MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**3. Exotic couplings bn angular correlation within the SM beyond the SM**

(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 MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**a in GT : 6He Paul trap @ GANIL**

“ideal” 3D Paul trap First transparent prototype Fully transparent trap (rings) URF ring hat RFQ cooler buncher MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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LPCTrap results GOAL: Measure the bn angular correlation in 6He decay with (Da/a)stat < 0.5% First data taking run in [X. Fléchard et al., PRL101 (2008) ] All position sensitive detectors; complete kinematics neutrino mass TOF (2008): collected 4×106 (for stat) and 2×106 (for sys studies) events. Statistical precision reached; data analysis under way. MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**a in Fermi : WITCH Penning trap @ ISOLDE**

(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 First recoil ion spectrum Retardation potential (V) 124Sn recoils [V.Yu. Kozlov et al., NIM B 266 (2008) 4515] Too low 35Ar production/transport so far System being upgraded MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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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 MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Constraints on Scalar couplings**

[J.C. Hardy and I.S. Towner, PRC 79 (2009) ] MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Constraints on Tensor couplings**

A in 114In MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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**Constraints on sums of exotic couplings**

MESON 2010, Cracow, June 10-16, O. Naviliat-Cuncic

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