The threshold energy of the C 12 (He 3 ,w)0 14 reaction has been measured precisely with the use of a Van de Graaff accelerator and an electrostatic analyzer, the value being 1436.2±0.9 kev. From this value, the O 14 beta-decay end-point energy (for decay leading to the 2.312-Mev state in N 14 ) is computed to be 1.8000 ±0.0065 Mev, based on the 1956 table of masses, and 1.8097 ±0.0015 Mev, based on the 1960 table of masses. A revised value of the Fermi interaction constant in beta decay is calculated and applied in the conserved vector current theory of Feynman and Gell-Mann. When (1) the radiative corrections and other corrections are applied to the decay of O 14 , (2) the corrected ft value is used to compute the vector coupling constant in beta decay, (3) the value of this vector coupling constant is assumed to be the same as that for the muon decay and is used to calculate the lifetime of the muon, and (4) this lifetime is corrected for radiation effects, the predicted mean life of the muon becomes 2.289±0.013 jusec (based on the 1960 table of masses and the radiative corrections of Kinoshita and Sirlin) or 2.245±0.013 //sec (based on the 1960 table of masses and the corrections, radiative and otherwise, of Durand and collaborators). The former value is 3.6% greater than a weighted average of several recent measurements of the muon mean life, 2.210±0.003 jusec, while the latter value is only 1.6% greater, and is within the combined experimental and theoretical uncertainties. However, the definitions of coupling constants used by Durand and collaborators differ somewhat from those used by others.
Yield curves have been calculated for (p,n) threshold reactions and the results have been applied to data previously obtained with the two-meter electrostatic analyzer at the Naval Research Laboratory. Taken into account in the calculation are the finite beam-energy spread from the analyzer, Doppler broadening due to thermal motion of the target nuclei, and the effect due to the statistical nature of the energy loss of protons in the target. A comparison of the yield-curve shape when the cross section is proportional to the emitted neutron velocity and the yield-curve shape when there is a nearby resonance is made. There is a small but calculable difference between the extrapolated yield curve intercept and true threshold energy. The threshold energies for several reactions are determined from data previously reported: T 3 (p,n)He s , 1019.76±0.51 keV; Li 7 (M)Be 7 , 1881.27±0.94 keV; C 13 (;M)N 13 , 3237.1=bl.6 keV.
B591
The d + d -d + p + n breakup reaction was studied over a range of bombarding energies Ed = 14-36 MeV. The proton and deuteron were detected at angle pairs chosen to either emphasize quasifree scattering (QFS) or the n-p final-state interaction (FSI). It was found that by using a smooth cutoff for the deuteron wave function, a modified plane-wave impulse-approximation(PODIA) theory could fit the magnitude and shape of the observed QFS peaks. To fit the QFS plus FSI data only triplet FSI was needed in contrast to some earlier results that indicated a strong singlet FSI. The singlet FSI contribution to the cross sections was estimated to be less than 1% in all cases studied.
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