Neutron density distributions in $^{40,42,44,48}$Ca observed via polarized proton elastic scattering at 300MeV

Systematic behaviors of neutron densities in $^{40,42,44,48}{\rm Ca}$ have been deduced via proton elastic scattering at $E_p=300{\rm MeV}$. For the deduction we used RIA with medium modified {\it NN} interaction and realistic point proton density distributions unfolded from charge distributions. In this work we have taken into account the effect of intrinsic charge distribution inside neutron as well as that of proton, which makes the proton distributions more gradual and the RMS radius larger than the case only proton charge assumed. We have observed that the isotope shift of neutron density distributions due to the occupation of the 1$f_{7/2}$ neutron orbit is seen around 3 fm and $^{48}$Ca has a large neutron skin of $\sim 0.2$ fm compared with the other three Ca isotopes.