βν angular correlations
in nuclear β-decay
Oscar Naviliat-Cuncic
Laboratoire de Physique Corpusculaire de Caen (IN2P3/CNRS-ENSICAEN)
and
Université de Caen Basse-Normandie
context and motivation
• searches for signatures of new physics beyond the Standard Model
of electroweak interactions.
credo:
• evidence for “new physics” should manifest itself either at the
high energy frontier (direct production of new particles) or at the
precision frontier (search for tiny effects).
• look anywhere one can look for (atomic, nuclear, particle
physics);
• here: nuclear β-decay.
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 3
allowed β-decay phenomenology
• within the SM
low momentum
transfer:
4-fermion point-
like interaction
• beyond the SM
include all Lorentz invariants
i = S, P, V, A, T
Ci and C’i relative (complex) strengths: 20 – 1 = 19 real parameters
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 4
scenarios beyond SM
• leptoquark exchange • limits on MLQ
bosons which induce quark-lepton transitions
assume standard couplings:
• carry lepton and baryon numbers
• have fractional |Q| = 1/3, 2/3 charges
• have spin J = 0,1 (in minimal extensions)
• A.G. Adelberger et al., PRL 83 (1999) 1299 (Fermi):
MLQ > 400 GeV
• R. Huber et al., PRL 90 (2003) 202301-1 (GT):
MLQ > 560 GeV
direct searches:
• K. Hagiwara et al., PRD 66 (2002) 010001 (PDG):
MLQ > 200-300 GeV
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 5
correlations and coefficients
• the simplest β-decay kinematic vectors
n → p + e− + ν e Jn
Pp
σe
pν pe
• from unpolarized nuclei, with no sensitivity to the electron polarization
b : interference term
a : angular correlation coefficient
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 6
the βν angular correlation
• within the SM
Fermi fraction
mixing ratio
• beyond the SM
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 7
sensitivity to exotic couplings
• Fermi transitions recoil spectrum
• Gamow-Teller transitions
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 8
traps for correlation experiments
• clean source
• ions (almost) at rest
• well localized in space
• matter free (allowing direct detection of recoil ions)
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 9
candidate and implementation
• Gamow-Teller transition
• produce 6He nuclei
• trap (radioactive) ions
(requires beam cooling)
• measure 6Li recoil (or TOF)
(ER < 1.4 keV)
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 10
realization near SPIRAL at GANIL
RFQ pulse down Paul trap
low cooler/buncher
energy
production
• 3x108 ions/s
• E = 10 – 30 keV
• 80π mm.mrad
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 11
buffer gas cooling of ions
• fast cooling technique (radioactive ions)
• RF field (0.5-2.0 MHz): radial confinement
• buffer gas: dissipation
• longitudinal driving electric field
• potential well: bunch formation
(G. Darius et al., accepted for publication in RSI)
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 12
cooling of 4He+ ions
tests at LIMBE/GANIL
(G. Ban et al., NIM A518 (2004) 712)
• 4He+ ions at 10 keV
• measure TOF after exctraction
105 ions/bunch; FWHM 100ns
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 13
the Paul trap
• 3D confinement requires oscillating field
electrostatic potential
URF
hat
ring
• the transparent Paul trap (J. Pinard, Orsay)
• trapping of Al+ and Mo+ , from plasma source (1999-2000)
• trapping of Na+ after cooling in H2, e-/ionization (2002)
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 14
6Li+ ions trapping
• the new Paul trap: just rings
• open acces for injection
• open acces for detection
• freedom to monitor phase space
• trapping of 6Li+ ions after cooling in H2 gas (50 pA incident current)
TOF distributions…cooling in the trap, in agreement with simulations
decay time = 200 ms
Number of ions (x 10 )
4
2
1
0
0 100 200 300 400 500
trapping time (ms)
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 15
the trap chamber
10cm PMT
plastic
scintillator
SSD
µCP
6He+
ion cloud monitor
“back-to-back” geometry µCP
recoil ion detector
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 16
the detectors
• SSD 60x60 mm2: ∆x = ∆y = 1mm (300 µm) 0,7
6 +
0,6 Li
• CH2 scintillator
absolute efficiency
0,5
0,4
0,3
0,2
0,1
0,0
0 1 2 3 4 5
energy (keV)
1,05
• position sensitive µCP
relative efficiency
∆t = 200 ps FWHM; ∆x=∆y < 200 µm 1,00
0,95
0,90
5,0 5,5 6,0 6,5 7,0 7,5
energy (keV)
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 17
systematic effects and SM theory
• ion cloud phase space • radiative corrections:
• influence of RF fields ( order α and Zα2)
(F. Glück, NP A628(1998)493)
• effect of residual gases
• detector response functions
• …
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 18
status
• cooling of 4He+ demonstrated: 5-10% transmission
• trapping of 6Li+ demonstrated: 25-30% efficiency
• full setup now installed on the LIRAT line near SPIRAL
• monitoring of ion cloud in progress
• first in trap coincidences expected in 2004-05
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 19
related projects
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 20
people and support
G.Ban, G.Darius, P.Delahaye1, D.Durand, X.Flécahrd, M.Herbane,
M.Labalme, E.Liénard, F.Mauger, A.Méry, O.Naviliat-Cuncic, D.Rodriguez
Laboratoire de Physique Corpusculaire de Caen, France
1 CERN-ISOLDE, Geneva, Switzerland
6th Framework Program:
INPC-2004, Göteborg, June 29th, 2004 O.Naviliat-Cuncic: naviliat@lpccaen.in2p3.fr 21