ftValue ofO14and the Universality of the Fermi Interaction

Abstract

The conserved-vector-current theory of the strangeness-conserving weak decays predicts that Gv, the vector coupling constant in nuclear beta decay, should be equal to G>, the coupling constant in the muon decay. To make possible a more precise comparison of Gv and G>, the ft value of O 14 has been remeasured. The endpoint energy of the positron decay has been determined by measuring the Q values of the reactions C 12 (He»0 14 and C 12 (He 3 ,^)N 14 * (2.311-MeV state), using the same techniques and equipment where possible in order to minimize the uncertainty in the difference of the Q values. The results of these measurements are Q n = -1148.8±0.6 keV and &=2468.4=b 1.0 keV, which yield £max(0 + ) = 1812.6±1.4 keV, all energies relative to the Li 7 (M) Be7 threshold assumed as 1880.7d=0.4 keV. The half-life of O 14 has also been remeasured as 71.00±0.13 sec, which implies a partial halflife of 7l.43±0.15 sec for the transition to the 2.311-MeV state of N 14 . Averaged with the recent half-life measurement of Hendrie and Gerhart, we obtain an ft value of 3075±10 sec for the O 14 decay, after correcting for nuclear form factors, electron screening, and if-capture competition. With the radiative corrections of Kinoshita and Sirlin, the value obtained for G v is (1.4025 ±0.0022) X 10~4 9 erg-cm 3 , where the quoted error is experimental in origin. This is to be compared with the value computed from recent muon decay measurements, G>= (1.4312=1=0.0011) X10~4 9 erg-cm 3 , which is (2.0=1=0.2)% larger. As there appear to be several possible theoretical explanations for this small discrepancy, the present results are consistent with the conserved-vector-current hypothesis.

Superallowed0+→0+nuclearβdecays: 2014 critical survey, with precise results forVud

“…Thus the value for C S /C V in Eq. (19) applies equally well to the ratio m e f S /g V . Expressed as a limit at the 90% confidence level, we obtain m e f S g V < 0.0035 .…”

Superallowed0+→0+nuclearβdecays: A new survey with precision tests of the conserved vector current hypothesis and

“…(19)-from which to determine two parameters, |V ud | and |V us |. We perform a nonlinear least squares fit to obtain the result |V ud | = 0.97424 (22), |V us | = 0.22534 (93). (20) Note that the value of |V ud | obtained from this fitting procedure has only changed by one unit in the last figure compared to Eq.…”

“…We argue that if the experimental f t values agree with the calculations where the nucleus-to-nucleus variations are large, then that must surely verify the calculations' reliability for the nine cases whose corrections are considerably smaller. Already four cases of this type have been carefully measured: 22 Mg, 34 Ar, 62 Ga, and 74 Rb. They appear to agree well with the calculations although, with the exception of 62 Ga, their uncertainties are still five times greater than those for the best known transitions.…”

Study of ¹⁴O as a test of the unitarity of the CKM matrix and the CVC hypothesis

“…Sidhu and Gerhart use the weighted average total halflife result from Bardin [41] and Hendrie and Gerhart [42] of 71.36 ± 0.09 seconds to obtain the branching ratio. The…”