Nuclear de-excitations in low-energy charged-current <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>ν</mml:mi><mml:mi>e</mml:mi></mml:msub></mml:math> scattering on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ar</mml:mi><mml:mprescripts/><mml:none/><mml:mn>40</mml:mn></mml:mmultiscripts></mml:math>
S. Gardiner
Abstract
Background: Large argon-based neutrino detectors, such as those planned for the Deep Underground Neutrino Experiment, have the potential to provide unique sensitivity to low-energy (few to tens of MeV) electron neutrinos produced by core-collapse supernovae. Despite their importance for neutrino energy reconstruction, nuclear de-excitations following charged-current ${\ensuremath{\nu}}_{e}$ absorption on $^{40}\mathrm{Ar}$ have never been studied in detail at supernova energies.Purpose: I develop a model of nuclear de-excitations that occur following the $^{40}\mathrm{Ar}({\ensuremath{\nu}}_{e},{e}^{\ensuremath{-}})^{40}\mathrm{K}^{*}$ reaction. This model is applied to the calculation of exclusive cross sections.Methods: A simple expression for the inclusive differential cross section is derived under the allowed approximation. Nuclear de-excitations are described using a combination of measured $\ensuremath{\gamma}$-ray decay schemes and the Hauser-Feshbach statistical model. All calculations are carried out using a novel Monte Carlo event generator called MARLEY (Model of Argon Reaction Low Energy Yields).Results: Various total and differential cross sections are presented. Two de-excitation modes, one involving only $\ensuremath{\gamma}$ rays and the other including single neutron emission, are found to be dominant at few tens-of-MeV energies.Conclusions: Nuclear de-excitations have a strong impact on the achievable energy resolution for supernova ${\ensuremath{\nu}}_{e}$ detection in liquid argon. Tagging events involving neutron emission, though difficult, could substantially improve energy reconstruction. Given a suitable calculation of the inclusive cross section, the MARLEY nuclear de-excitation model may readily be applied to other scattering processes.