Nuclear density dependence of polarization transfer in quasi-elastic A ( e , e ′ p ) reactions

Le résumé fourni par la source

The ratio of the transverse and longitudinal components of polarization transfer to protons in the quasielastic $(\stackrel{P\vec}{e},{e}^{\ensuremath{'}}\stackrel{P\vec}{p}\phantom{\rule{0.16em}{0ex}})$ reaction, ${P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}}$, is sensitive to the proton's electromagnetic form factor ratio, ${G}_{E}/{G}_{M}$. To explore density-dependent in-medium modifications, a comparison of polarization transfer ratios involving protons from distinct nuclear shells, each with different local nuclear densities, has been proposed. In this study, we present such comparisons between four shells, $1{s}_{1/2},1{p}_{3/2}$ in $^{12}\mathrm{C}$ and $1{d}_{3/2},2{s}_{1/2}$ in $^{40}\mathrm{Ca}$. In an effort to account for other many-body effects that may differ between shells, we use a state-of-the-art relativistic distorted-wave impulse-approximation (RDWIA) calculation and present the double ratios ${({P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}})}_{\mathrm{Data}}/{({P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}})}_{\mathrm{RDWIA}}$ as well as the super-ratios ${[{({P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}})}_{\mathrm{A}}/{({P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}})}_{\mathrm{B}}]}_{\mathrm{Data}}/{[{({P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}})}_{\mathrm{A}}/{({P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}})}_{\mathrm{B}}]}_{\mathrm{RDWIA}}$, for chosen shells A and B, as a function of effective local nuclear densities. We find that double ratios for individual shells show a dependence on the probed effective nuclear densities. Studying the super-ratios, we observed a systematic variation between pairs of higher- and lower-density shells.

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