Low-energy atmospheric neutrino flux calculation with accelerator-data-driven tuning

Abstract

We have incorporated a hadron interaction tuning based on accelerator data into our atmospheric neutrino flux calculation, which has been used to analyze atmospheric neutrino oscillations at Super-Kamiokande. This new approach enables a more direct evaluation of the flux uncertainty than a conventional tuning using atmospheric muons. The neutrino flux calculated with this new tuning is 5\%--10\% smaller but still consistent with our previously published prediction within its uncertainty. The flavor ratio $(\nu_{\mu}+\bar{\nu}_{\mu})/(\nu_e+\bar{\nu}_e)$ and $\bar{\nu}/\nu$ ratios were consistent with the previous prediction. Based on the measurement errors of the accelerator data, we evaluated the flux uncertainty associated with the new tuning to be 7\%--9\% in the $E_{\nu} <$ 1 GeV region, which was difficult to assess with the conventional tuning. The flux uncertainty in the $1<E_{\nu}<10$ GeV region was evaluated to be 5\%--7\%, which is an improvement over the conventional tuning.