The beta decay asymmetry parameter of 35Ar

The beta decay asymmetry parameter for 35Ar = 35Cl + e+ + nu/sub e/ has been remeasured in order to resolve a long standing puzzle. Previous asymmetry measurements, when combined with the comparative half-life, yield a value for the vector coupling constant, G/sub v/, that is in serious disagreement with the accepted value. We produced polarized 35Ar by a (p,n) reaction on 35Cl using the polarized proton beam provided by Lawrence Berkeley Laboratory's 88-Inch Cyclotron. The polarization of the 35Ar was determined by measuring the asymmetry of the positrons produced in 35Ar decay to the first excited state in 35Cl (branching ratio = 1.3%) in coincidence with a 1219.4 keV gamma ray. Our result, A0 = 0.49 +- 0.10, combined with the comparative half-life yields a value for G/sub v/ in agreement with the accepted value