Quark substructure approach to 4He charge distribution

Abstract

We present a study of the ${}^{4}$He charge distribution based on realistic nucleonic wave functions and incorporation of quark substructure. Any central depression of the proton point density seen in modern four-body calculations is too small by itself to lead to a correct description of the charge distribution of ${}^{4}$He if folded with a fixed proton size parameter, as is usually done. We utilize six-quark structures calculated in the chromodielectric model for $N$-$N$ interactions to find a ``swelling'' of the proton size as the internucleon distance decreases. This swelling is a result of the short-range dynamics in the $N$-$N$ system. Using the independent pair approximation, the corresponding charge distribution of the proton is folded with the two-nucleon distribution generated from Green's function Monte Carlo calculations of the ${}^{4}$He nucleonic wave function. We obtain a reasonably good fit to the experimental charge distribution of ${}^{4}$He. Meson-exchange currents have not been included.