Beta Neutrino Correlation Measurement with Trapped Radioactive Ions Gilles BAN LPC Caen, CNRS/IN2P3, Caen, France

Outline Motivation Context How to measure, Traps Status Conclusion

 decay to probe the weak interaction precise measurement of:  decay, probe V-A interaction Allowed transitions, unpolarized nuclei : a v W(E, θ) = W(E) [1 + e cos( q m ) + b ] c E - angular correlation coefficient a For example pure Gamow Teller transition (6He) : SM : Ci = - Ci’ real CT = 0 aGT = -1/3 Any deviation -> Tensor (GT), Scalar (Fermi) contribution -> New physics Any observable linked to  gives access to the parameter a

Context Still up to ~ 5 to 10% of non SM contribution Several measurement with traps Goal : a measurement with a precision below 1% Traps = excellent tool for measurements Matter free Clean environment Well localized source b and recoil detection

Context North america atom traps Triumf, Berkeley 38Km 0.3% scalar PRL 94, 142501 (2005) 21 Na 0.5% mix PRL 93, 102501 (2004) Europe Ion traps Cern, Ganil … For the T contribution « old experiment » Johnson 1963 1% PR 132 1149 (1963)

Correlation Measurement with 6 Helium -Pure Gamow-Teller transition (J = +1) -100% G.S to G.S. -Reasonable Half life = 0.8 s - High Q=3.51 MeV-> Tmax =1.4 keV - GANIL production rate: 108 pps

GANIL accelerators complex LIRAT LPCTrap Production target ECR source Specific Low Energy beamline for Precision Measurement with traps LIRAT Beams characteristics : 10-30 keV, 80 p mm mrad rate : ~ 108 ions/s

LPC TRAP no strong magnetic field (b) ions « at rest » in vacuum ions well localized open geometry : high detection solid angle Cooling and bunching of He collimators Paul trap as precision measurement trap - recoil ion coincidences measurements

Beamline and set up

Trap, Cooler, detectors 20 cm

Status 1998 : Start, 2003 : He cooling with H2, 2004 : Beamline completed 2005 : Commissioning run at GANIL with 6He+ -> proof of principle -> b-recoil coincidences measured from an ion trap 2006 : First data taking run (1 week) Data Out of trap decay Acc. coincidence ToF (ns) Counts -> 105 coincidences [(Da/a)stat ~ 2 %] -> LPCTrap efficiency ~ 5 10-3 % (tduty = 100 ms) -> main systematic effects identified - BG - trapped cloud imagery - detectors response & position, … 8/12

LPCTrap efficiency ~ 5 10-2 % (tduty = 100 ms) 2007-2008 : Optimization & improvement -> fine tuning of the whole setup with 6Li1+ ions (F. Duval, NIM B (2008) ) -> adding of a vacuum impedance to decrease the background -> measurement of ion cloud size (D. Rodríguez, Hyp. Int. 174 (2007)) -> precise alignement of the detectors (1/10 mm) -> adding of a 90° recoil detector -> measurement of plastic scintillator response function with e- spectrometer (Bordeaux) -> … Test in july 2008 with 6He (Ibeam ~ 4 107 pps) Raw data ~2 hours Counts LPCTrap efficiency ~ 5 10-2 % (tduty = 100 ms)  ~ 4 coincidences/s ToF (u.a.) 10/12

One week run with optimized set up ~60 000 events/h October 2008 One week run with optimized set up ~60 000 events/h 4 106 events recorded !! Statistical accuracy reach Analysis and systematics Underway… n mass reconstruction with cloud size, ion temp, BG, Out of trap, BS Geometry, shake off… ~2hours run

Conclusion Precision experiments at low energy are a powerfull tool to probe the SM b-n Correlations with traps LPC TRAP fully working and complete 6He correlation , statistics acquired (~0,5%), analysis underway, precision? other experiments with the set up

THANKS for YOUR ATTENTION !!

GANIL: Jean-Charles Thomas LPCTrap: Gilles Ban Dominique Durand Florian Duval Xavier Fléchard Etienne Liénard François Mauger Oscar Naviliat-Cuncic Philippe Velten Ex-postdoc/students Mustapha Herbane Daniel Rodriguez Guillaume Darius Pierre Delahaye Alain Mery GANIL: Jean-Charles Thomas

19Ne, 35Ar : other candidates available @ LIRAT b+ emitters e- shake off measure Mirror decays (F + GT) r = GT/F determination + precise T1/2 Vud in CKM matrix… - Alternative to 0+ -> 0+ - Competitive with n decay see arXiv:0809.0994 in http://arxiv.org/ : "Determination of |Vud| from nuclear mirror transitions" by O. Naviliat & N. Severijns LPCTrap facility is available to anyone interested by SPIRAL beams… 12/12