Aβ[Eβ] in 37K decay: new physics with opposite β helicity
Abstract
By extending our analysis and simulations of our 37K β-decay data set to allow the β asymmetry with respect to nuclear spin to vary with β energy Eβ, we have gained sensitivity to new physics that depends on a helicity factor for the β, mβ/Eβ. In particular, we constrain Lorentz scalar and tensor quark-lepton interaction strengths at a sensitivity complementary to the similar Fierz interference term in neutron β decay. Our result for that new physics is a Fierz interference term b = 0.033 0.084 (stat) 0.039 (syst), consistent with the standard model electroweak interaction value b=0. We consider presently achieved complementarity to β-decay and particle physics experiments, along with projectable technical improvements to our method.
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