Speaker
Description
In the standard electroweak model, the weak current with a Vector – Axial-vector (V-A) form explains the weak interaction in a phenomenological context. However, the Lee-Yang Hamiltonian conserving Lorentz symmetry allows right-handed (V+A) as well as scalar, and tensor currents. For decades there have been efforts searching for such exotic currents as a test of the standard model. In particular, beta decay has been a powerful tool since the exotic currents are related to its kinematics [Ja57]. Furthermore, its precision is comparable with high energy physics experiments [Go19].
The WISArD experiment, succeeding the WITCH experiment, has carried out the weak interaction studies at the ISOLDE facility. We employ the beta-delayed proton emission of 32Ar to search for a scalar current in beta-neutrino correlations. The extent of the proton kinetic energy shift provides information indirectly on the kinematics of beta-decay recoil nuclei, which is different between scalar- and vector-type interactions.
In the WISArD setup, the 30-keV 32Ar+ ions are implanted in the catcher foil at the center. The positrons emitted upwards are guided by the field of a superconducting magnet and detected by a scintillator. Silicon detectors surrounding the catcher foil measure the kinematic shift of the beta-delayed protons. A proof-of-principle campaign was executed in 2018 [Ar20] and reached the 3rd best value for the angular correlation coefficients of vector decays. After upgrading the apparatuses, the first part of a new experiment was done in October 2021. We present details of the experimental devices and recent technical development for the setup.
References
[Ja57] J. D. Jackson, S. B. Treiman, and H. W. Wyld, Phys. Rev. 106, 517 (1957).
[Go19] M. Gonzàlez-Alonso et al, Prog. Part. Nucl. Phys. 104, 165 (2019).
[Ar20] V. Araujo-Escalona et al., Phys. Rev. C 101, 055501 (2020).
