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asymmetry parameter measurements
in nuclear -decayas a probe for
non-Standard Model physics
K.U.Leuven, Univ. Bonn, NPI Rez (Prague), ISOLDE
CERN - INTC 15 November 2004
N. Severijns
STRUCTURE OF THE WEAK INTERACTION IN NUCLEAR BETA DECAY
general Lorentz invariant 4-fermion interaction
h.c. n| |p )( e e5'
i iiii OCCOH
Fermi, 1933 : 4-fermion interaction
Lee & Yang, 1956; Wu et al., 1957 :parity violation
with i = Scalar, Vector, Tensor, Axial vector, Pseudoscalar
and coupling constants Ci defining properties of the interaction types
In the Standard Model :
* CV = 1 (CVC)
* CA = -1.27 ( gA/gV = -1.2697(6) from n-decay )
* CV’ = CV & CA
’ = CA (maximal P-violation)
* CS = CS’ = CT = CT
’ = CP = CP’ 0 (only V- and A-currents)
experimental upper limits:
(neutron and nuclear -decay)
* no time reversal violation (except for the CP-violation described by the phase in the CKM quark-mixing matrix)
/ 0.08
/ 0.06 (95% CL)
T A
S V
C C
C C
from: N. Severijns, M. Beck, O. Naviliat-Cuncic,
Rev. Mod. Phys., accepted
Limits (95 % CL) on possible new bosons for S- and T-interactions, from high-energies:
mass limit for H± (charged Higgs) : > 79.3 GeV (LEP-ALEPH)
mass limit for leptoquarks : > 242 GeV (from pair production; combined CDF-D0)
: > 298 GeV (from single production; ZEUS)
Limits for fT from K± decay [Particle Data group, Phys. Lett. B592 (2004) 1 ] :
|fT / f+| = 0.012(23) from K±e3 decay |fT / f+| < 0.058 (95% C.L.)
|fT / f+| = 0.001(7) from K±3 decay |fT / f+| < 0.015 (95% C.L.)
J
-asymmetry
for a pure Gamow-Teller transition :
(assuming maximal P-violation and T-invariance for V- and A-interactions)
-0.008 < Im (CT+C’T)/CA < 0.014 (90% CL) from 8Li @ PSI, R. Huber et al., PRL 90 (2003) 202301
A/A = 0.01 (for m/Ee 0.5) Re [(CT+CT’) / CA] < 0.040 (95% CL)
recoil corr. (induced form factors) 10-3 (see below) ; radiative corrections 10 -4
AGT independent of nuclear matrix elements
( ) = 1 e
pW J A
E
' 'T T T T
J'JA A
C + C C + C 1 + Im Re
C CGTe
αZm γmA
p E
J'J
2
= 1 for J J 1
J = for J J+1
J+1
= 1 ( Z)
Low Temperature Nuclear Orientation
@ NICOLE
N(θ)( ) 1 cos
N(θ)pol
GTunpol
vW k A P Q
c
cf. IS349 – IS381
,J'J
J'J
1 Re GT T T
AGT
A C Cm m
E E CA
N(θ)( ) 1 cos
N(θ)pol
GTunpol
vW k A P Q
c
cos[ ( ) 1]
[ ( ) 1] cos
vA P Q
W c
vW A P Qc
'T T
J'JA
C + C 1 + Re
CGTγm
AE
1. Absolute measurements
2. Relative measurements
from Geant and
experimental data
cosv
Qc
First case: 114In
1+ 0+ pure GT
E0 = 1.99 MeV
log ft = 4.473(5)
E = 1.70 – 1.85 MeV
= -1.017(20)GTA
N. Severijns, submitted for publication
(m/E = 0.210)
- 0.24 < Re (CT+C’T)/CA < 0.08 (90% CL)
( best precision for A for a fast pure GT transition to date ! )
Isotope transition Eendpoint
(keV)
m/E@
endpoint
AGT log ft recoil correction
*)
P (%)@
10 mK
typeof
meas.
79Kr +, 1/2- 3/2- 604 0.44 -0.333 5.62(12) 54
85mKr -, 1/2- 3/2- 840 0.36 +0.333 5.252(6) 61
79Kr/ 85mKr 0.80 -1 -0.015(5) rel.
67Cu -, 3/2- 5/2- 576 0.43 0.600 6.3 0.004(3) 76 abs.
82gBr -, 5- 4- 444 0.52 -1 5.048(8) -0.004(2) 87 abs.
83Br -, 3/2- 1/2- 931 0.34 -1 5.03(4) -0.005(3) 98 abs.
Proposal
*) due to weak magnetism and induced tensor form factors
if A/A = 0.01 | Re (CT+C’T)/CA |< 0.02 to 0.04 (90% CL)
Other experiments
1. Leuven - AGT
60Co and 133Xe, with LTNO and 15 T external magnetic field instead of hyperfine field
( I.S. Kraev, N. Severijns et al., in preparation )
2. Los Alamos - AGT
82Rb in MOT atom trap; m/E = 0.13
( S.G. Crane et al., Phys. Rev. Lett. 86 (2001) 2967 - D.J. Vieira et al., Hyp.Int. 127 (2000) 387 )
3. LPC-Caen (O. Naviliat et al) - aGT
6He in Paul ion trap
( P. Delahaye al., Hyp.Int. 132 (2001) 479 )
All experiments are aiming at a precision of 0.5% to 1% !
Beam shifts purpose
79Kr 2 AGT
85mKr 8 AGT
67Cu 1 AGT
68Cu 4 implantation quality
82gBr 1 AGT
83Br 10 AGT
82Sr 1 calibrate Geant
118Te (or 118Xe ) 1 calibrate Geant
Total = 28
Beam time request