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

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 $σ(E)$ 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 $σ(E)$ 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 $σ(E)$ 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 $(ν, n)$ and $(ν, 2n)$ 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.

Figures (3)

• Figure 1: Diagram of charge-exchange excitations in the ${}^{127}$I($\nu_{e}$, $e^{-}$)${}^{127}$Xe reaction with decays of high-lying excitations in ${}^{127}$Xe into ${}^{126}$Xe and ${}^{125}$Xe isotopes with the emission of one and two neutrons with the corresponding energies $S_{1n}$ and $S_{2n}$, respectively. In the left part is the spectra of solar (up to 18 MeV) and the green line is accelerator neutrinos up to 55 MeV.
• Figure 2: (a) Energy spectra of solar Bahcall_book and accelerator PhysRevD.106.032003 neutrinos. (b) Charge-exchange strength function $S(E)$ for the excitation of Gamow--Teller and analog resonances in ${}^{127}$I. Blue solid lines present experimental data on the ${}^{127}$I($p, n$)${}^{127}$Xe reaction Palarczyk_PhysRevC.59.500, black solid line presents our calculation within the theory of finite Fermi systems (TFFS), and dotted lines correspond to the GTR-1, GTR-2, PR1, PR2, and PR3 resonances.
• Figure 3: Integral $I(E_{max})$ given by Eq. (\ref{['eq:Mi_summ']}) versus the energy $E_{max}$ for the ${}^{127}$Xe isotope: (steps) experimental data from Palarczyk_PhysRevC.59.500, (solid line) calculation with $e_q = 1.0$, dotted line -- calculation with $e_q = 0.9$, (dash-dotted line) calculation with $e_q = 0.8$, and (horizontal straight line) sum-rule value of $3(N - Z) = 63$. The scale on the abscissa axis changes after 20 MeV.