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Neutrino excitation of nuclear levels in /sup 12/C and /sup 16/O

Thesis/Dissertation ·
OSTI ID:6235974
While the neutrino excitation of nuclear levels is an interesting subject per se, its understanding becomes equally important for all those neutrino-induced elementary-particle reactions where complex nuclei are present in the counters and/or target materials. In the present approach, the neutrino cross sections for a /sup 12/C and /sup 16/O target with excitation of all known T = 1 levels of /sup 12/N or /sup 16/F respectively, are calculated employing a phenomenological approach. Specifically, fits to the measured electroexcitation form factors of the T = 1 levels in /sup 12/C and /sup 16/O are obtained with the help of the generalized Helm model. The results obtained are subsequently employed in predicting the neutrino cross sections of the /sup 12/C and /sup 16/O analog states in /sup 12/N and /sup 16/F both in the low and high neutrino energy regime. In order to perform the calculations, the cross section for the neutrino induced nuclear reactions is expressed in terms of a multipole expansion appropriate for the excitation of nuclear levels of definite spin and parity. The multipole expressions thus obtained are of general validity, independent of any nuclear model, but simplify upon use of the Helm model. The needed nuclear transition densities are obtained from parameterizing the fits of the electroexcitation form factors in terms of a small number of strength, radius and smearing width parameters. These same parameters are then employed in the neutrino cross section calculations. Since the nuclear transition densities thus obtained are semiempirical, employing as much as possible experimental data, the problem of overestimating the cross sections is removed.
Research Organization:
Catholic Univ. of America, Washington, DC
OSTI ID:
6235974
Country of Publication:
United States
Language:
English