On scattering cross sections and durations near an isolated compound-resonance, distorted by the non-resonant background, in the center-of-mass and laboratory systems

TL;DR

This paper investigates how scattering cross sections and time delays near compound-resonances behave differently in the center-of-mass and laboratory systems, revealing a phenomenon where time delay turns into time advance in the C-system, but not in the L-system.

Contribution

It introduces and applies non-standard analytical transformations of cross sections from the C-system to the L-system, clarifying the differences in resonance phenomena between the two systems.

Findings

Time advance appears instead of delay in the C-system near resonances.

In the L-system, the delay-advance phenomenon does not occur.

Calculated cross sections in the L-system agree with experimental data for several nuclei.

Abstract

During last 20 years there was revealed and published the phenomenon of the appearing of the time advance instead of the time delay at the region of a compound-nucleus resonance, distorted by the non-resonant background (in the center-of-mass (C-) system). This phenomenon is usually accompanied by a minimum in the cross section near the same energy. Here we analyze the cross section and the time delay of the nucleon-nucleus scattering in the laboratory (L-) system. In the L-system the delay-advance phenomenon does not appear. We use and concretize the non-standard analytical transformations of the cross section from the C-system to the L-system, obtained in our previous papers. They are illustrated by the calculations of energy dependences of cross sections in the L-system for several cases of nucleon elastic scattering by nuclei 12C, 16O, 28Si, 52Cr, 56Fe and 64Ni at the range of distorted resonances in comparison with the experimental data.