Precision half-life measurement of 29P.

A new precision half-life measurement of 29P was conducted using the TwinSol β-counting station at the University of Notre Dame Nuclear Science Laboratory. The resulting value of t1/2new=4.1055(44)s is the most precise 29P half-life measurement to date. Utilizing this measurement and reevaluating the world data leads to a new world average of t1/2world=4.1031(58)s, which improves the Birge ratio from 3.11 to 1.45 and is 2.3 times more precise than the previous world value. The new Cabibbo-Kobayashi-Maskawa matrix element Vud for 29P shifts closer into agreement with the superallowed pure Fermi value. The uncertainty in the mixed transition value of Vud, however, is still dominated by the Fermi to Gamow-Teller mixing ratio ρ. Using the new world half-life and assuming the validity of the standard model, a new predicted value for ρ and its associated correlation parameters have been evaluated in order to guide future determination of ρ. [ABSTRACT FROM AUTHOR]