Physics of two-nucleon system by polarized beam and polarized targets

Recent progress on the studies of dibaryons is reviewed. The pp resonances 1D2 and 3F3 have been almost established by the recent measurement of the difference of longitudinal polarization total cross sections at SIN and LAMPF and the difference of transverse polarization total cross sections at TRIUMF. The Argand diagram obtained by several groups also supported the presence of these resonances. Apart from these, 3P2 and 3F4 resonances were suggested by the Argand diagrams, and 3D2 and 1P1 were predicted at low energy theoretically. It is favorable to regard the dibaryons as the new state of hadrons. This was supported by the indication of the existence of the 1F3 resonance with the minus parity at M = 2.21 GeV, which was suggested by the partial wave analysis of np world data. This resonance was supported by the measurement of the difference of longitudinal polarization total cross sections (I=O) at ANL and np reaction cross section (I=O) by the Freiburg group. The measurement of the differential cross section of np scattering in the forward direction was recommended as a proposal at KEK. The perfect experiment of n-p scattering using polarized beam available in future is recommended. (Ito, K.)