Zemach and Friar radii of the proton and neutron from lattice QCD

We present the first lattice-QCD result for the Zemach and Friar radii of the proton and neutron. Our calculation includes both quark-connected and -disconnected diagrams and assesses all sources of systematic uncertainties arising from excited-state contributions, finite-volume effects and the continuum extrapolation. At the physical point, we obtain for the proton $r_Z^p=(1.013\pm 0.010(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.012(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}))\mathrm{f}\mathrm{m}$ and $r_F^p=(1.301\pm 0.012(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.014(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}))\mathrm{f}\mathrm{m}$. These numbers suggest small values of the Zemach and Friar radii of the proton, but are compatible with most of the experimental studies.