Measurement of shell energies for $^{40,48}$Ca by using ($\vec{p},2p$) reaction

The binding energies and the spectroscopic factors of the proton orbits in $^{40}$Ca and $^{48}$Ca nuclei were measured by using ($\vec{p}$,2$p$) reaction at 200MeV. The aim of this experiment is to investigate the neutron-number dependence of the shell energies, which is motivated by a recent theoretical work $[1]$ on the monopole effect of the tensor force. Since the ($\vec{p}$,2$p$) reaction shows clear $j$-dependence at this energy, unambiguous $j$-assignment is expected. The experiment was performed at RCNP using a two-arm spectrometer system. The energy resolution achieved was better than 200keV FWHM. In the presentation, comparison of the present result with a previous ($\vec{d}$,$^3$He) result $[2]$ will be also given. \\[4pt] [1] T. Otsuka $et al.,$ Phys. Rev. Lett. $\textbf{95}$ (2005) 232502.\\[0pt] [2] S. M. Banks $et al.,$ Nucl. Phys. $\textbf{A437}$ (1985) 381.