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

2. Outline
Motivation Context
How to measure, Traps
Status
Conclusion

3.  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

4. 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

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

6. 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

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

8. 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

9. Beamline and set up

10. Trap, Cooler, detectors
20 cm

11. 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 ~ % (tduty = 100 ms)
-> main systematic effects identified
- BG - trapped cloud imagery
- detectors response & position, …
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12. LPCTrap efficiency ~ 5 10-2 % (tduty = 100 ms)
: 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 ~ pps)
Raw data
~2 hours
Counts
LPCTrap efficiency ~ % (tduty = 100 ms)
 ~ 4 coincidences/s
ToF (u.a.)
10/12

13. One week run with optimized set up ~60 000 events/h
October 2008
One week run with optimized set up
~ 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

14. 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

15. THANKS for YOUR
ATTENTION !!

16. 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

17. 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: in :
"Determination of |Vud| from nuclear mirror transitions"
by O. Naviliat & N. Severijns
LPCTrap facility is available to anyone interested by SPIRAL beams…
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