Precise measurement of the angular correlation parameter a_βν in the β decay of ³⁵Ar with LPCTrap

¹ LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France
² Instituut voor Kern- en Stralingsfysica, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
³ GANIL, CEA/DSM-CNRS/IN2P3, Caen, France
⁴ CIMAP, CEA/CNRS/ENSICAEN, Université de Caen, Caen, France
⁵ NSCL and Department of Physics and Astronomy, MSU, East-Lansing, MI 48824, USA
⁶ Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, 18071 Granada, Spain

^a e-mail: fabian@lpccaen.in2p3.fr

Published online: 20 March 2014

Abstract

Precise measurements in the β decay of the ³⁵Ar nucleus enable to search for deviations from the Standard Model (SM) in the weak sector. These measurements enable either to check the CKM matrix unitarity or to constrain the existence of exotic currents rejected in the V-A theory of the SM. For this purpose, the β-ν angular correlation parameter, a_βν, is inferred from a comparison between experimental and simulated recoil ion time-of-flight distributions following the quasi-pure Fermi transition of ³⁵Ar¹⁺ ions confined in the transparent Paul trap of the LPCTrap device at GANIL. During the last experiment, 1.5×10⁶ good events have been collected, which corresponds to an expected precision of less than 0.5% on the a_βν value. The required simulation is divided between the use of massive GPU parallelization and the GEANT4 toolkit for the source-cloud kinematics and the tracking of the decay products.