Abstract
Precise measurements in the β decay of the 35 Ar 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 35 Ar1+ 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.
Highlights
Physics beyond the Standard Model (SM) may be searched through high or low energy experiments [1]
This paper will focus on the latter case and on observations of β decay processes
The LPCTrap group started a new simulation from scratch using the modular Bayeux/Cadfael package developped by the SuperNEMO collaboration [11] which will be used to wrap GEANT4 and other tools
Summary
Physics beyond the Standard Model (SM) may be searched through high or low energy experiments [1]. The Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix is expected to be unitary The energy distribution of the recoiling daughter ion is sensitive to aβν To reach this observable, it is not possible to use classical calorimetry since the recoil ions have a very low kinetic energy (a maximum of 450 eV in the case of 35Ar). It is not possible to use classical calorimetry since the recoil ions have a very low kinetic energy (a maximum of 450 eV in the case of 35Ar) This is why time-of-flight (TOF) measurements were chosen, where the detection of the ultrarelativistic β particle signals the start while the recoil ion detector provides the stop. The shakeoff is especially important for the 35Ar1+ ion study since its sole β+ decay leads to a neutral 35Cl species, nearly impossible to detect
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