We report first measurements of the $\beta$-neutrino angular correlation based on the kinetic-energy shift of protons emitted in parallel or antiparallel directions with respect to the positron in the beta decay of ${}^{32}\mathrm{Ar}$. This proof of principle experiment performed at ISOLDE-CERN provided simultaneous measurements for both a superallowed $0^{+}\to 0^{+}$ transition and a Gamow-Teller transition followed by proton emission. The results, respectively ${\tilde{a}}_{\beta \nu }=1.007{\left(32\right)}_{\mathrm{stat}}{\left(25\right)}_{\mathrm{syst}}$ and ${\tilde{a}}_{\beta \nu }=-0.222{\left(86\right)}_{\mathrm{stat}}{\left(16\right)}_{\mathrm{syst}}$, are found in agreement with the standard model. The analysis of the data shows that future measurements can reach a precision level of ${10}^{-3}$ for both pure Fermi and pure Gamow-Teller decay channels, providing new constraints on exotic weak interactions.

• Received 11 June 2019
• Revised 27 February 2020
• Accepted 13 April 2020

DOI:https://doi.org/10.1103/PhysRevC.101.055501