respectively, in the kinematics relevant for the MAMI A1 apparatus [@A1] (three upper panels), and for MESA at 80 MeV (lower panel).[]{data-label="sensitivity"}](sigma180mev_22deg.pdf "fig:"){width="7.5cm"} ![(Color online) Sensitivity to the variation of the parameter $a_1$ entering $f_T^{PWBA}$ in the range \[0.99, 1\] and $a_2$ entering $f_T^{FSI}$ in the range \[180, 250\] is shown by the dashed and solid lines, respectively, in the kinematics relevant for the MAMI A1 apparatus [@A1] (three upper panels), and for MESA at 80 MeV (lower panel).[]{data-label="sensitivity"}](Sensitivity_a1_180mev_16deg.pdf "fig:"){width="7.5cm"} ![(Color online) Sensitivity to the variation of the parameter $a_1$ entering $f_T^{PWBA}$ in the range \[0.99, 1\] and $a_2$ entering $f_T^{FSI}$ in the range \[180, 250\] is shown by the dashed and solid lines, respectively, in the kinematics relevant for the MAMI A1 apparatus [@A1] (three upper panels), and for MESA at 80 MeV (lower panel).[]{data-label="sensitivity"}](Sensitivity_a1_80mev_16deg.pdf "fig:"){width="7.5cm"}

To bring the discussion to a more quantitative level, we list the projected impact of a $d(e,e')pn$ measurement in several kinematics of A1 and MESA for the uncertainty of the dispersion calculation of the Lamb shift in Table \[tab3\]. For this analysis, we assumed for simplicity that the uncertainty of the fit will be equal to the precision of the data.[^1] For the 