Study of  - correlations with LPCTrap Dominique Durand LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France On behalf of the LPCTrap collaboration Laboratoire de Physique Corpusculaire - Caen

Outline  Motivation  Physics case and measurement principle  Experiments and results  Summary EXON 2012

STANDARD MODEL of Particle Physics is a very powerful and predictive model (recent Higgs probable discovery) but it is probably not complete Questions: mass hierarchy, strong CP problem, matter/anti-matter, dark energy/matter Test at low energy: high precision measurements search for very small deviations from SM predictions EDM’s, correlations (A, a, b, B, D, R, ….), g-2… search for very rare (presumably forbidden) processes neutrinoless double  decay, proton decay, … High precision and high energy experiments are complementary

observables linked to  are sensitive to a  Recoil Ion (RI) momentum spectrum Measurement of the beta neutrino angular correlation parameter a  E  : energy and velocity of the beta particle W o (E  ): phase space distribution as given by the Fermi theory of beta decay  : angle between the antineutrino and beta particle 2+ +   decay rate:  decay and the weak interaction

SM Test  pure vector axial interaction theory study through  decay a  is a function of the coupling constants Gamow-Teller  Axial / Tensor Fermi  Vector / ScalarCL : 95.5% Exotic currents (beyond SM) tensor/scalar Goal: new physics or Improve constraints on couplings  decay, Vector -Axial, a   - angular correlation coefficient measurement a  with relative statistical uncertainty less than 0.5% deviation from a  =-1/3 or 1 (SM) might reveal existence of new particles: leptoquark bosons … a  (C V, C S, C A, C T, M F, M GT ) :  angular correlation parameter Pure F : a F (C V, C S ) = +1 (SM, C S = 0) Pure GT : a GT (C A, C T ) = -1/3 (SM, C T = 0)

Mirror transitions : Analysis of available data (5 nuclei) competitive with neutron/pion decay Valuable alternative to 0+->0+ transitions Several parameters to be measured: T 1/2, BR, Q,  and to be computed (corrections) Transition|V ud | Super-allowed pure Fermi Super-allowed mirror Neutron Pion (22) (17) (19) (30) & a   = (1-  ²/3)/(1+  ²) For mirror transitions :  =GT/F O. Naviliat Cuncic et al., PRL102 (2009) CKM matrix and a  Proceedings of CKM2010, the 6th International Workshop on the CKM Unitarity Triangle. T Sparado, A. Young

observables linked to  are sensitive to a  Recoil Ion (RI) momentum spectrum Ion trapping techniques are universal (several nuclei) - LPCTrap: a  deduced from RI ToF measurement - ions almost at rest and well localized - open configuration, few dead zones Precision measurement  a  / a  <1%: very difficult experiment: systematic effects such as the RF field  ToF spectrum deformation «shake-off» ionization probability required How to measure a  Transparent Paul Trap

V-A 6 He + pure GT transition, tensor coupling a  =-1/3 High Q value, RI ( 6 Li) up to 1.4 keV T 1/2  high rate and efficient transmission to the trap V ud and V-A 35 Ar +, Mirror 35 Cl n+ scalar coupling, mixed transition  corrections a  =0.904 High Q value but heavier ion RI ( 35 Cl) up to 450 eV T 1/2  high rate and efficient transmission to the trap Other candidates: 19 Ne, 37 K, 39 Ca Nuclei of interest

SPIRAL 6 He beam 10 keV  E ~ 20eV Paul trap Effective potential 1-2 V Beam- handling Beam characteristics : keV, 80  mm mrad - rate : ~ 10 8 ions/s LIRAT Production target ECR source LPCTrap

Beam line preparation Ions bunches Cycle period: 200ms (accumulation) Beam 6 He + ~ He + /s ~ He + /s trapped ions Total efficiency: ~ RFQCB: High-voltage platform  Buffer-gas cooling technique: H 2 or He  Ion bunches Continuous voltage: longitudinal confinement RF field: radial confinement Cycle period: 200ms (accumulation) 1meter

Detectors and trap Detection in coincidence of recoil ion (RI) and  particle ToF measurement (  detection: START, RI detection: STOP) Post-acceleration between the two collimators (Installed 2009) 50 cm free flight tube  charge state separation (identified by ToF) Time of flight: Free flight tube MCP Beta position E β Recoils --  telescope 6 He + bunch Charge state separation: Free flight tube MCP with delay line anode MCPPSD Ion trap Silicon + plastic scintillator + PMTPost-acceleration

Recoil ion detector design Grounded collimator Grid MCPPSD Acceleration electrode Collimator Focusing electrode LPCTrap : simultaneous measurement of a  and the «shake-off»probability Focusing electrode to collect recoil ions with maximal efficiency Geometry design and bias voltages estimation with “SIMION” software Successfully tested during four days in November 2010

6 He + :experimental results ( ) P shake-off = (35) stat (07) syst PRL (Couratin et al.) 108 (2012) Vise (coincidence) Result: a  = (73) stat (75) syst SM value = -1/3 PRL (Fléchard et al.) 38 (2011) (  a  /a  ) stat ~2% Improve statistics also improve systematic uncertainties - effect of ion cloud temperature  effect of  back-scattering 6 He+ Pure GT Limit on Tensor 10 5 events

6 He + : experimental results ( ), shake off Complete Monte-Carlo simulation w/ all systematic effects: RF fields, ion cloud characteristics, detectors response functions... Experimental spectrum fit w/ P shake-off as free parameter assuming a  = -1/3 Experiment: ~4 days, Intensity ~10 8 pps, ~ «true» coincidences High precision:  P shake-off = Excellent agreement: theoretical value of P shake-off = (35) stat (07) syst PRL (Couratin et al.) 108 (2012) “exceptional research” from APS Data analysis still in progress GOAL: a  estimation Preliminary: agreement w/ SM value Relative stat. uncertainty < 0.5% Li 3+ Li 2+

35 Ar + : experiments results ( ) 2011 commissioning run 2 days days expected final uncertainty   a  (stat) < full analysis is underway 35 Cl charge state distribution Ar + /s incoming beam with ~2.5 x 10 8 contaminants/s x 10 4 trapped 35 Ar + ions (every 200 ms)

Implantation tape station Multi Reflection Time Of Flight Mass Spectrometer (MR-TOF-MS needed for new beams) t accu ~ 1-10ms t accu ~ 100ms Main RFQ Small RFQ ("rebuncher") New chamber PREMS: re-submitted to the ANR At least a factor ~ 10 in statistics

 Precision measurement of the  -decay of exotic nuclei can probe the weak interaction part of the Standard Model: a    V-A, V ud  LPCTrap is a universal tool that measures accurately a   for several nuclei of interest and provide shake-off probabilities Near future: Ne19 experiment accepted by GANIL PAC  Future: new beams and new apparatus - PREMS: renewal of the experimental set-up on the LIRAT beam line - new exotic beams and facilities are needed  Summary & future plans

LPC CAEN : Claire Couratin (PhD-2013) Dominique Durand Xavier Fabian (PhD-2015) Xavier Fléchard Etienne Liénard François Mauger Oscar Naviliat-Cuncic Gilles Quéméner Philippe Velten (PhD-2011) GANIL:Pierre Delahaye Bertrand Jacquot Jean-Charles Thomas CIMAP:Alain Méry and the LPC technical staff also thanks to the GANIL beam operators KUL Leuven: Martin Breitenfeldt Simon Van Gorp Tomika Porobic Nathal Severijns

EXON 2012 WITCH ISOLDE CERN Measure a  with a precision better than 0,5 % ISOLDE+ REXTRAP (beam handling) Penning traps Retardation spectrometer Main isotope 35 Ar + Scalar searches

EXON 2012 WITCH ISOLDE CERN After solving all kind of problems Local penning, mechanical… Data Obtained in 2011 with 35 Ar a  = 1.12 (33) stat SM value of a =0.9004(16 ). Still a lot to measure and simulate Next run Oct 2012

EXON 2012 We are not alone… From N. Severjins, KUL