A MICROSCOPIC DESCRIPTION OF POLARISATION PHENOMENA IN THE FOUR NUCLEON SYSTEM

Publisher Summary This chapter presents a microscopic description of polarization phenomena in the four nucleon system. A continuum treatment of the excitations in the mass-4 system using the coupled channels method provides a satisfactory description of different aspects of the experimental data. The results obtained from the coupled channels model for the energy dependence of the neutron polarization P n observed Haight in the reaction t (p,n) 3 He. Below 3 MeV proton energy the calculations confirm that the value of P n is determined essentially by the interference effects between the 3P 0 and 3P 2 amplitudes. In a study described in the chapter, in the 3–5 MeV region, the cross-over to negative values took place at energy below that observed experimentally. If the 1 −1 , T = 0 resonance was shifted to about 24 MeV, the agreement with experiment was considerably improved. Beyond 5 MeV, calculations involving only the negative parity resonances gave values of P n that were generally well below experiment. A positive parity T=0 resonance was reported experimentally around 25 MeV in 4 He.