The subtraction contribution to the muonic-hydrogen Lamb shift: A point for lattice QCD calculations of the polarizability effect

The proton-polarizability contribution to the muonic-hydrogen Lamb shift is a major source of theoretical uncertainty in extraction proton charge radius. An empirical evaluation this effect, based on structure functions, requires systematically improvable calculation "subtraction function", possibly using lattice QCD. We consider different subtraction point, with aim accessing function directly calculations. A useful feature point that corresponding functions suppressed. whole effect dominated by contribution, calculable lattice.