Study of two nucleon emission mechanism by using tagged photons and continuous electron beams in the intermediate energy region.

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Study of the two nucleon emission mechanism have been performed by using toe continuous electron beam at Laboratory for Nuclear Science, Tohoku University (Kakuriken). In the photon energy range above the giant dipole resonance and below the pion threshold, the direct nucleon emission and two nucleon photoabsorption process dominate the reaction process, because the effects of the nuclear collective motion and the isobar and strongly suppressed. It has been suggested that investigations of two nucleon angular and energy correlation from the final nuclear states may provide informations of correlated nucleons and meson exchange effect. In this project, in order to obtain a efficient coincidence measurements, a large solid angle proton detector system has been build. This system is consisted of 30 pair of E-E type plastic counter telescopes whose total solid angle is 1.02 sr and energy resolution is 5-10% of the proton energy.The measurements were carried out at the Tagged Photon Facility whose energy range of the quasi-monoenergetic photon was 24 to 102 MeV. The differential cross sections of (gamma,n,), (gamma,p), (gamma,np) and (gamma,pp) on ^4He, ^<6,7>Li and ^<10>B targets were measured.In the low missing energy region, single nucleon emissions from the s- and p-shell orbit were investigated. The momentum distributions of these nucleons were deduced by means of quasi-free-knockout analysis. The momentum region was 200-450 MeV/c corresponding to much higher region than the presently obtainable momentum range by (e,e'N) experiments. in the high missiong energy region, two nucleon emission dominates the reaction process. The angular correlation between emitted neutrons and protons has shown a similar shape with the deuteron photo-disintegration kinematics. This fact indicates the importance of the photoabsorption by a correlated nucleon pair inside the nucleus.