The T2K Neutrino Flux Prediction

TL;DR

The paper details the T2K neutrino flux prediction method, combining simulations and experimental data to accurately model neutrino production and estimate uncertainties for oscillation studies.

Contribution

It introduces a comprehensive flux prediction approach using FLUKA, GEANT3, and NA61/SHINE data, achieving uncertainties below 15% near the flux peak.

Findings

Flux prediction uncertainty below 15% near peak

Far-to-near flux ratio uncertainty less than 2%

Effective modeling of hadronic interactions

Abstract

The Tokai-to-Kamioka (T2K) experiment studies neutrino oscillations using an off-axis muon neutrino beam with a peak energy of about 0.6 GeV that originates at the J-PARC accelerator facility. Interactions of the neutrinos are observed at near detectors placed at 280 m from the production target and at the far detector -- Super-Kamiokande (SK) -- located 295 km away. The flux prediction is an essential part of the successful prediction of neutrino interaction rates at the T2K detectors and is an important input to T2K neutrino oscillation and cross section measurements. A FLUKA and GEANT3 based simulation models the physical processes involved in the neutrino production, from the interaction of primary beam protons in the T2K target, to the decay of hadrons and muons that produce neutrinos. The simulation uses proton beam monitor measurements as inputs. The modeling of hadronic interactions is re-weighted using thin target hadron production data, including recent charged pion and kaon measurements from the NA61/SHINE experiment. For the first T2K analyses the uncertainties on the flux prediction are evaluated to be below 15% near the flux peak. The uncertainty on the ratio of the flux predictions at the far and near detectors is less than 2% near the flux peak.