Effect of High-Lying Resonances on Cross Sections for Solar-Neutrino Capture by $${}^{\mathbf{127}}$$I Nuclei

Abstract

The resonance structure of the charge-exchange strength function $$S(E)$$ and its effect on the cross sections for solar-neutrino capture by $${}^{127}$$ I nuclei are analyzed. Three types of isobaric resonances are studied within the self-consistent theory of finite Fermi systems. These are the giant Gamow–Teller resonance; the analog resonance; and the pygmy resonances, which lie lower. The capture cross section $$\sigma(E)$$ for solar neutrinos incident to $${}^{127}$$ I nuclei is calculated with allowance for the resonance structure of the strength function $$S(E)$$ , and the effect of each resonance on the energy dependence $$\sigma(E)$$ is analyzed. It is shown that all high-lying charge-exchange resonances should be taken into account in calculating the cross section $$\sigma(E)$$ . The contributions of neutrinos of different origin to the structure of the cross section $$\sigma(E)$$ are analyzed. In particular, the contribution of energetic neutrinos to the ratio of the $${}^{127}$$ Xe and $${}^{126}$$ Xe production rates is considered. The $${}^{126}$$ Xe $$/^{127}$$ Xe isotope ratio is an indicator of hard boron neutrinos in the solar spectrum.