New experimental constraints on polarizability corrections to hydrogen hyperfine structure

We present a state-of-the-art evaluation of the polarizability corrections–the inelastic nucleon corrections–to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value ${\mathrm{\Delta }}_{\mathrm{p}\mathrm{o}\mathrm{l}}=1.3\pm 0.3$ ppm. This is 1–2 ppm smaller than the value of ${\mathrm{\Delta }}_{\mathrm{p}\mathrm{o}\mathrm{l}}$ deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits.