A. García

Positron-Neutrino Correlation in the 0 + → 0 + Decay of 32 Ar

4 pages, 1 table, 4 figures.-- PACS nrs.: 23.20.En, 13.30.Ce, 23.40.Bw, 24.80.+y.-- Erratum to this paper in: Phys. Rev. Lett. 83(15): 3101-3101 (1999).The positron-neutrino correlation in the 0[sup +][r arrow]0[sup +] [beta] decay of [sup 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[plus minus]0.0052[plus minus]0.0039 , which yields improved constraints on scalar weak interactions. [copyright] [ital 1999] [ital The American Physical Society]

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

The positron–neutrino correlation in the 0+→0+ β-decay of 32Ar was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of the narrow proton group following the super-allowed decay. Our result is consistent with the standard model prediction;for vanishing Fierz interference we find a=0.9989±0.0052±0.0039. Our result leads to improved constraints on scalar weak interactions. The positron–neutrino correlation in 33Ar decay was measured in the same experiment;for vanishing Fierz interference we find a=0.944±0.002±0.003. The 32Ar and 33Ar correlations, in combination with precision measurements of the half-lives, super-allowed branching ratios and beta endpoint energies, will determine the isospin impurities of the super-allowed transitions. These will provide useful tests of isospin-violation corrections used in deducing |Vud| which currently indicates non-unitarity of the KM matrix.

Measurement of gamow-teller strength for 176Yb --> 176Lu and the efficiency of a solar neutrino detector

We report a 0 degrees 176Yb(p,n)176Lu measurement at IUCF where we used 120 and 160 MeV protons and the energy dependence method to determine Gamow-Teller (GT) matrix elements relative to the model independent Fermi matrix element. The data show that there is an isolated concentration of GT strength in the low-lying 1(+) states making the proposed Low Energy Neutrino Spectroscopy detector (based on neutrino captures on 176Yb) sensitive to pp and 7Be neutrinos and a promising detector to resolve the solar neutrino problem.

Positron-Neutrino Correlation in the 0[sup +][r arrow]0[sup +] Decay of [sup 32]Ar

4 pages, 1 table, 4 figures.-- PACS nrs.: 23.20.En, 13.30.Ce, 23.40.Bw, 24.80.+y.-- Erratum to this paper in: Phys. Rev. Lett. 83(15): 3101-3101 (1999).The positron-neutrino correlation in the 0[sup +][r arrow]0[sup +] [beta] decay of [sup 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[plus minus]0.0052[plus minus]0.0039 , which yields improved constraints on scalar weak interactions. [copyright] [ital 1999] [ital The American Physical Society]