Wigner time delay of particles elastically scattered by a cluster of zero-range potentials

The Wigner time delay of slow particles in the process their elastic scattering by compound targets consisting several centers modeled zero-range potentials is studied. It shown that at asymptotically large distances from target, Huygens-Fresnel interference pattern formed spherical waves emitted each transformed into a system generated geometric center target. These wave functions determine flow inward and outward through surface sphere surrounding energy derivatives phase shifts these are partial delays. General formulas, which establish relationship between $s$-phase particle shift cluster potentials, have been obtained. clusters two, three, four were considered as model targets. centers, equally distant other, assumed to be described same delta-function potentials. delays scattered evaluated. derived general formulas applied both processes electron atomic trapping electrons \ensuremath{\pi}-meson on few-nucleon systems.