Speaker
Dr
Etienne Lienard
(LPC Caen)
Description
The precise measurement of the beta-neutrino angular correlation coefficient "a" in nuclear beta decay is a sensitive tool to search for exotic couplings presently excluded by the V-A theory of the weak interaction. For instance, the study of a pure Gamow-Teller (GT) transition enables to probe tensor-type couplings while a pure Fermi (F) transition is sensitive to scalar-type interactions. Moreover, in the case of mirror transitions, a precise measurement of "a" also allows the determination of the mixing ratio between the GT and F contributions. This constitutes an important input for the database of nuclear mirror transitions, leading to the extraction of the Vud element of the CKM matrix [1].
In a beta-neutrino correlation measurement, the most relevant observable is the energy of the recoiling daughter nucleus. In the LPCTrap device, the radioactive nuclei are confined in a Paul trap, allowing the detection of the recoil ions in coincidence with the beta particles [2]. The set-up is presently installed at LIRAT, the low energy beam line of the SPIRAL facility at GANIL. The correlation measurement in the pure GT 6He decay has already reached a relative statistical precision of 0.5%. Particular attention is continuously being devoted to the study of systematic effects. For instance, the detection set-up is sensitive to the charge state distributions of the recoiling ions, allowing the determination of the shake-off probabilities in the decay of 1+ ions.
As the Paul trap enables to confine any radioactive species, an experiment with 35Ar, which essentially decays through a mirror transition with a large Fermi component (>90%), is also ongoing.
These first experiments have clearly shown that LPCTrap is well suited for precise correlation measurements. The next step is a significant upgrade of the whole set-up to improve, on one hand, the statistical precision to the 0.1% level and, on the other hand, to perform relevant experiments with the future radioactive beams soon available at GANIL in the framework of the SPIRAL/GANISOL initiative, and later at the SPIRAL2/DESIR facility.
These different aspects will be discussed during the conference.
[1] O. Naviliat-Cuncic and N. Severijns, Phys. Rev. Lett. 102 (2009) 142302
[2] X. Fléchard et al., J. Phys. G: Nucl. Part. Phys. 38 (2011) 055101
Primary authors
Ms
Claire Couratin
(LPC Caen)
Dr
Etienne Lienard
(LPC Caen)
Dr
Xavier Flechard
(LPC Caen)
Co-authors
Dr
Alain Mery
(CIMAP)
Dr
Daniel Rodriguez
(Universidad de Granada)
Dr
Dominique Durand
(LPC Caen)
Prof.
Gilles Ban
(LPC Caen)
Dr
Gilles Quemener
(LPC Caen)
Dr
Jean-Charles Thomas
(GANIL)
Dr
Martin Breitenfeldt
(IKS-KUL)
Prof.
Nathal Severijns
(IKS-KUL)
Prof.
Oscar Naviliat-Cuncic
(NSCL-MSU)
Dr
Pierre Delahaye
(GANIL)
Mr
Simon Van Gorp
(IKS-KUL)
Mr
Tomica Porobic
(IKS-KUL)
