RECONSTRUCTION OF THE ANALYTIC S-MATRIX FROM EXPERIMENTAL-DATA AND ENERGY-DEPENDENT PHASE-SHIFT ANALYSIS FOR D(4)HE SCATTERING

Final results of long-term work of the united group from Nuclear Physi cs Institute (Moscow State University) and Institute for Nuclear Resea rch (Russian Academy of Sciences) on developing a general procedure fo r reconstructing the analytic S matrix directly from experimental data by means of an energy-dependent phase-shift analysis are reported as applied to d(4)He scattering in the energy range 0-10 MeV. The resulti ng partial S matrix is used to refine the parameters of the low-energy resonances (+)0, 2(+)0, and 1(+)0 and to determine reliably the verte x constant of the virtual decay Li-6(1(+)0) --> He-4 + d. Some importa nt physical aspects of composite-particle interaction are discussed in the context of these results. It is shown that, in the case of not ve ry narrow resonances, resonance parameters determined with the aid of the standard single-level approximation of the R matrix differ signifi cantly from the values obtained by means of a direct analytic continua tion to a complex Breit-Wigner pole.