Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing

A. Garcia; E. G. Adelberger; C. Ortiz; H. E. Swanson; M. Beck; O. Tengblad; M. J. G. Borge; I. Martel; H. Bichsel; the Isolde Collaboration

doi:10.1023/a:1012605731737

arXiv · nucl-ex/9904001

Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing

A. Garcia·E. G. Adelberger·C. Ortiz·H. E. Swanson·M. Beck·O. Tengblad·M. J. G. Borge·I. Martel·H. Bichsel·the Isolde Collaboration

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Abstract

The positron-neutrino correlation in the 0^+ \to 0^+ βdecay 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. Our result leads to improved constraints on scalar weak interactions. The positron-neutrino correlation in ^{33}Ar decay was measured in the same experiment; for vanishing Fierz interference we find a=0.944 \pm 0.002 \pm 0.003. The ^{32}Ar and ^{33}Ar correlations, in combination with precision measurements of the half-lives, superallowed branching ratios and beta endpoint energies, will determine the isospin impurities of the superallowed transitions. These will provide useful tests of isospin-violation corrections used in deducing |V_{\rm ud}| which currently indicates non-unitarity of the KM matrix.

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A. Garcia, E. G. Adelberger, C. Ortiz, H. E. Swanson, M. Beck, O. Tengblad, M. J. G. Borge, I. Martel, H. Bichsel, the Isolde Collaboration. 1999-04-01. Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing. https://doi.org/10.1023/a%3A1012605731737

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