The positron-neutrino correlation in the $0^+ to 0^+ beta$ decay of $^{32}$Ar was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of the narrow proton group following the superallowed decay. Our result is consistent with the Standard Model prediction. For vanishing Fierz interference we find $a=0.9989 pm 0.0052 pm 0.0036$, which yields improved constraints on scalar weak interactions.
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