Simultaneous measurements of the beta-neutrino angular correlation in Ar-32 pure Fermi and pure Gamow-Teller transitions using beta-proton coincidences

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 Ar-32. This proof of principle experiment performed at ISOLDE-CERN provided simultaneous measurements for both a superallowed 0(+) -> 0(+ )transition and a Gamow-Teller transition followed by proton emission. The results, respectively (a) over tilde (beta nu) = 1.007(32)(stat) (25)(syst) and (a) over tilde (beta nu) = -0.222(86)(stat) (16)(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.