Reconsideration of the Electron-Neutron Scattering Length As Measured by the Scattering of Thermal Neutrons by Noble Gases

Abstract

Our value for the electron-neutron scattering length has been corrected on the basis of new measurements of some neutron scattering lengths and now is (-1.30±0.03) ×${10}^{-16\mathrm{}}$ cm, which is 3% lower than our original result. (The equivalent figure in the Fermi convention is -3630±70 eV and at $q=0\mathrm{}$, $\frac{d{G}_{\mathrm{En}}}{d{q}^2}=0.0189\mathrm{}\pm 0.0004$ ${\mathrm{fm}}^2$.) A check on the worrisome possibility of an ${\mathrm{H}}_2$ impurity in the scattering gases showed that is quite unlikely to be a significant source of error. The difference between our result and the Munich measurement and also the Foldy calculation thus continues unexplained.