Speaker
Description
The Standard Model as a very succesful theory of electroweak interactions postulates the basic assumption about the pure „V(ector)-A(xial vector)“ character of the interaction. Nevertheless, other types of weak interactions (Scalar, Tensor) are still not experimentally ruled out. Low-energy searches for these „forbidden components“ studying e.g. . β-ν angular correlations in β-decay are complementary to high-energy experiments e.g. at the LHC. The experimental program WISArD (Weak-Interaction Studies with 32Ar Decay) situated at the isotope separator ISOLDE/CERN searches for these S/T currents in the weak interaction (or at least tries to significantly improve their current experimental limits) via the precise study of the kinematic shift of β-delayed protons emitted in the decay of 32Ar. Due to the presence of both Fermi and Gamow-Teller β-decays, both the S and T currents can be searched for simultaneously. The experimental apparatus consists of a cryostat with a superconducting 9T magnet and a dedicated system of particle detectors installed in the magnet bore around a thin catcher foil, where radioactive 32Ar ions delivered by ISOLDE are implanted. High precision measurements of the kinematic energy shifts of the protons emitted from the moving 32Cl nuclei recoiling after the β–decay of 32Ar carry information about β-ν angular correlations. The Fermi β-decay to the isobaric analogue state in 32Cl and Gamow/Teller β-decays to other states are sensitive to the possible admixture of S and T components, respectively, in the weak interaction. The experiment aims to reach a sensitivity limit of 0.1% on these exotic contributions to the weak interaction. After the successful proof-of-principle measurement performed in 2018 [1]. several major upgrades were installed [2] followed by another test measurement in 2021. Full data taking was performed in May 2024 and April 2025 aiming to reach a competitive result at the per-mil level of uncertainty for the angular correlation coefficients. The current status of the WISArD setup and newest experimental results will be presented. References: [1] V. Araujo-Escalona et al., Phys.Rev. C101(2020) 055501 [2] D. Atanasov et al., Nucl.Instr.Meth. A1050 (2023) 16159
