Interaction of accelerator neutrinos with energies up to 55 MeV with ${}^{127}$I nuclei

TL;DR

This study calculates and analyzes the cross sections of neutrino interactions with ${}^{127}$I nuclei at energies up to 55 MeV, considering high-lying resonances and comparing with experimental data.

Contribution

It introduces the first consideration of the high-lying analog resonance AR-2 in neutrino-${}^{127}$I interactions and assesses the contributions of various resonances to the cross section.

Findings

GTR-1 contributes 60-80% to the cross section.

GTR-2 contributes about 12%.

High-lying resonances cause discrepancies at energies above neutron separation threshold.

Abstract

The interaction of neutrinos with an energy of up to 55~MeV from the Spallation Neutron Source (SNS) accelerator with a perspective ${}^{127}$I detector at the Oak Ridge National Laboratory (United States) has been studied. The resonance structure of the charge-exchange strength function $S(E)$ has been calculated taking into account high-lying resonances, and the effect of this structure on the cross section $\sigma(E)$ for the accelerator neutrino capture by the ${}^{127}$I nucleus has been examined. The influence of the Gamow-Teller resonance GTR-1 and the second new higher resonance GTR-2 on the energy dependence of the cross section $\sigma(E)$ has been analyzed. The effect of the high-lying analog resonance AR-2 has also been taken into account for the first time. It has been found that the contributions of GTR-1 to the calculated cross section $\sigma(E)$ are from 60% to $\approx$80%, and GTR-2 about 12%, and AR-2 $\le$ 10%, respectively. The contribution of high-lying resonances to the $(\nu, n)$ and $(\nu, 2n)$ neutrino capture cross sections with neutron emission and the formation of the ${}^{126}$I and ${}^{125}$I isotopes, respectively, has been analyzed. The comparison of the cross sections for the interaction of accelerator neutrinos calculated by different methods with experimental data has shown coincidence at energies below the neutron separation threshold $E_x < S_{1n}$ and strong discrepancy at higher energies, which is difficult to explain. A new measurement of cross sections at energies $E_x > S_{1n}$ is needed.