# Etudes et tests preliminaires a une mesure de la correlation angulaire $\beta - \nu$ dans la desintegration du noyau $^{6}$He a l'aide d'un piege de Paul

Abstract : The subject of this thesis is the preparation of a measurement of the b-v angular correlation coefficient, in 6He nuclear fi - decay, using a Paul trap. Its principle consists in studying the decay of radioactive ions trapped in a small volume, practically at rest in the center of a transparent electric trap. The trajectories of the particles emitted in the decay are weakly disturbed. The detection in coincidence of the electron and the recoil ion in each decay allows the measurement of 3 observables: the energies of the particles and their relative angle. The b-v angular correlation parameter deduced from the coincidence spectrum is sensitive to the existence of exotic interactions excluded by the V—A theory of the weak interactions. In the case of 6He decay a deviation observed on the predicted value would imply the existence of tensor type interactions, which might be due to the exchange of leptoquarks. These are gauge bosons present in many extensions of the Standard Model. The work presented here concerns the tests of a transparent Paul trap. The performance of the trap has been tested with ions created in a laser plasma source (Mo+ , Fe+, Al+), and also with ions delivered by an ionization source (4He+ ions). These experiments were carried out in parallel with their simulations which required the development of a computer code of the electrical potential in various geometries, and of a code of ions transport in the associated fields. These simulations showed a good agreement with the experiment. A Monte Carlo simulation of the experimentalsetup, for the b-v angular correlation measurement, was then carried out. The distortions of the spectra associated with the varying electric fields in the vicinity of the trap and with the ion cloud size were estimated for various geometries. The statistical needs for the experiment were evaluated in order to reach the required precision.
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P. Delahaye. Etudes et tests preliminaires a une mesure de la correlation angulaire $\beta - \nu$ dans la desintegration du noyau $^{6}$He a l'aide d'un piege de Paul. Physique des Hautes Energies - Expérience [hep-ex]. Université de Caen, 2002. Français. ⟨in2p3-00011795⟩

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