Prediction of the NuMI electron and muon neutrino flux in ICARUS

The ICARUS experiment is a 430-ton liquid argon TPC neutrino detector at FNAL, measuring neutrinos from both the BNB and NuMI neutrino beams. It will soon be paired with the SBND detector in the BNB to search for sterile neutrinos and/or resolve existing sterile neutrino anomalies by using a near/far detector paradigm. ICARUS will begin its initial physics data run this Fall, where neutrino interaction data from both the BNB and NuMI beams can be used to measure neutrino-argon interaction cross-sections. Neutrinos from the NuMI beam incident upon ICARUS at a high off-axis angle of 5.7° will contribute a significant flux of muon and electron (anti-)neutrinos over an energy range that covers the DUNE first oscillation peak. Given the current dearth of neutrino-argon cross-section data, the ICARUS measurements will be an important input for DUNE near detector measurements, especially for setting initial ranges on systematic uncertainties.

As an essential first step toward performing a neutrino-argon cross-section measurement, this work aims to provide a comprehensive characterization of the NuMI neutrino flux prediction for ICARUS with its associated uncertainties. A Geant4-based flux simulation is augmented by applying corrections according to hadron cross-section models. The corrected flux, related uncertainties, and uncertainties due to beamline operating conditions were evaluated. The total uncertainty on the flux was found to be 10% (13%) for ν_e (ν_μ). The uncertainty on the ν_e/ν_μ flux ratio was additionally studied and found to be a factor 2 smaller than for the individual neutrino flavor modes.