Scattering and Reaction Cross Sections in the p + System with the Multiconfiguration Resonating-Group Method

Abstract

He cluster configurations, supplemented by their associated pseudo­ inelastic configurations. With the Minnesota nucleon-nucleon potential and a total of 25 cluster configurations, the results show that, with no adjustable parameters, the calculation can satisfactorily explain all the essential features of the measured scattering and reaction angular distributions, such as the angular positions of cross-section maxima and minima, the strong cross-section rise at backward angles, and so on. The only defect is that the calctdated values of the cross sections are on-the-average somewhat too large, which is correlated with the finding that the calculated p+ a total reaction cross sections are not yet large enough, being equal to only about 70-80% of the measured values. The way to improve the calculation is also discussed. The ultimate aim of an investigation with the resonating-group method 1 > (RGM) is to understand, in a completely microscopic way without any phenomenological adjustment, all the essential properties of the nuclear system under consideration. In particular, the experimental data on the total reaction cross section should be satisfac­ torily explained through the introduction of explicit reaction channels into the formu­ lation, rather than by the adoption of a phenomenologically determined imaginary potential which is an entity not compatible with the microscopic nature of the RGM. To achieve this aim, one must necessarily carry out the calculation in an extensive model space spanned by a sufficiently large number of cluster configurations, chosen according to physical intuition, energetical arguments, and the relative ease in the analytical derivation of the kernel functions. In the 6-nucleon system, for instance, a careful study 2 > has recently been performed, with the model space consisting of d +a, p+ 5 He and n+ 5 Li cluster configurations, supplemented by pseudo-inelastic configurations (PIC) involving pseudo-excited states of the deuteron cluster. The results obtained show that the d +a bound-state energy, differential scattering and reaction cross sections can all be well explained in a unified manner. The calculated d +a total reaction cross sections exceed 90 % of the measured values, indicating that the 6-nucleon calculation can be considered to be essentially complete.*> Similar *> The 6-nucleon calculation was performed with a purely central nucleon-nucleon potential in order to save computational effort. The use of a potential containing spin-orbit and tensor components will certainly be necessary for the discussion of the detailed features of the experimental data, but are not essential for extracting general information which is of interest to us, i.e., to study the cluster structures of bound and resonance levels, to determine the important mechanisms occurring in nuder reactions, and to learn the basic behavior of the intricate interplay among various cluster configurations.