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Theoretical study of pion nucleus reactions

Thesis/Dissertation ·
OSTI ID:5191640
The pion absorption reaction /sup 4/He(..pi../sup -/,n)/sup 3/H at T/sub ..pi../ = 290 MeV is studied with the effective channel formulation of high energy nuclear reactions applied to the ..pi../sup -/-/sup 4/He system to construct the full elastic scattering wave functions with explicit elastic and inelastic components. The ..pi..N interaction is taken to be an energy-dependent separable potential to account for the ..pi..N 33 resonance and a local Gaussian potential to produce the approximate spin and isospin average ..pi..N s-wave phase shifts and charge exchange cross section. To further study the pion absorption process, the ..pi..N potential parameters are adjusted to fit the ..pi../sup -/-/sup 4/He elastic scattering data. The kinematic transformation from the ..pi..N barycentric system to the ..pi../sup -/-/sup 4/He barycentric system is accomplished analytically and the resulting two channel system of coupled integro-differential equations is solved by iteration for T/sub ..pi../ = 260 MeV and compared with the experimental results for ..pi../sup -/-/sup 4/He elastic scattering at that energy. Without modification of the parameters of the ..pi..N potentials the ..pi../sup -/-/sup 4/He elastic scattering wave function at T/sub ..pi../ = 290 MeV is calculated and is used to evaluate the angular distribution of emitted neutrons in the pion absorption reaction /sup 4/He(..pi../sup -/,n)/sup 3/H to first order in the static form of the pion absorption operator. This treatment contains the ..pi../sup -/-/sup 4/He inelastic channel wave function explicitly and so is not the usual DWBA calculation. The n-/sup 3/H elastic scattering wave function is generated by the use of an optical potential. The calculated pion absorption angular distribution is compared with the experimental results at T/sub ..pi../ = 290 MeV. The inelastic component of the ..pi../sup -/-/sup 4/He elastic scattering state is found to be important for theta/sub CM/ greater than or equal to 30/sup 0/ in describing the distribution of emitted neutrons.
Research Organization:
Connecticut Univ., Storrs (USA)
OSTI ID:
5191640
Country of Publication:
United States
Language:
English