Neutron charge radius determined from the energy dependence of the neutron transmission of liquid208Pband209Bi

The ORELA experiment on the neutron charge radius has been reevaluated. The neutron transmission of liquid thorogenic ${}^{208}\mathrm{Pb}$ with the neutron time-of-flight method in the neutron energy range from 0.08 to 800 eV was measured. Additional studies on condensed matter effects for liquid Bi and liquid Pb have provided more accurate corrections resulting in smaller systematic uncertainties for the neutron-electron scattering length $b_{\mathrm{ne}}.$ We have also reevaluated the transmission data on liquid Bi of Melkonian and co-workers. We have obtained values of $b_{\mathrm{ne}}=(-1.33\pm 0.027\pm 0.03)\times {10}^{-3}\mathrm{fm}$ for ${}^{208}\mathrm{Pb}$ and $b_{\mathrm{ne}}=(-1.44\pm 0.033\pm 0.06)\times {10}^{-3}\mathrm{fm}$ for ${}^{209}\mathrm{Bi}$ where for both results the two uncertainties denote the statistical and the systematic uncertainty, respectively. The results for ${}^{208}\mathrm{Pb}$ and ${}^{209}\mathrm{Bi}$ were found to be in good agreement.