| Texto completo | |
| Autor(es): |
Santos, O. C. B.
;
Gomez-Camacho, J.
Número total de Autores: 2
|
| Tipo de documento: | Artigo Científico |
| Fonte: | PHYSICAL REVIEW C; v. 113, n. 1, p. 16-pg., 2026-01-12. |
| Resumo | |
A statistical method is presented to evaluate the uncertainty bands in the optical nucleus-nucleus potential and in differential cross sections. The starting point is the least square fit of a set of experimental values of elastic differential cross sections, varying the relevant optical potential parameters. This is done using standard chi 2 minimization codes, that provide the covariance matrix of the parameters. A maximum likelihood exploration of the chi 2 surface in parameter space allows us to determine the covariance matrix of the parameters associated to a contour of a given chi 2 value. The Bayes theorem allows us to assign probabilities (p values) to the regions in parameter space, characterized by chi 2 contours. The method allows us to obtain uncertainty bands of an arbitrary observable associated to a given p value using two approaches. The general approach determines the uncertainties from the extremes of the observables calculated in the region of parameter space associated to that p value. This requires an adequate sampling of parameter space, and explicit calculations of the observables on all sampling points. The simplified approach considers uncertainty propagation of the observable in terms of the optical model parameters. This involves the least square covariance matrix, given by chi 2 minimization codes, and analytically calculated enhancement factors for each p value. The method, in the general and simplified approaches, is applied to recent measurements of the elastic differential cross sections of 8Li + 58Ni. 1 sigma and 2 sigma uncertainty bands are obtained for the optical potentials as a function of the distance, and for the differential cross sections as a function of the angle. The general and simplified approaches are very similar in this case. The application of the procedure to determine uncertainty bands of complex scattering calculations is discussed. (AU) | |
| Processo FAPESP: | 19/07767-1 - Reações nucleares com núcleos fracamente ligados ou com estrutura de cluster, radioativos e estáveis |
| Beneficiário: | Leandro Romero Gasques |
| Modalidade de apoio: | Auxílio à Pesquisa - Temático |
| Processo FAPESP: | 21/12254-3 - Medidas exclusivas de reações nucleares com feixes de íons fracamente ligados estáveis e radioativos |
| Beneficiário: | Osvaldo Camargo Botelho dos Santos |
| Modalidade de apoio: | Bolsas no Brasil - Pós-Doutorado |