Extended Electromagnetic Structure Effects on Low-Energy Proton-Proton Scattering

The corrections to low-energy ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ $p-p$ scattering parameters, arising from the extended electromagnetic structure of the proton, are calculated in the context of nuclear-interaction models without a static core, with a soft core, and also with a hard core of radius $r_c=0.40\mathrm{}$ F. A comparison of the corrected ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ $p-p$ scattering length "neutralized" with an approximate formula ${\left(a_p\right)}^n$ is made with the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ $n-n$ scattering length $a_n$, recently determined by reliable experimental methods with reasonable accuracy.