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 $(ν_μ+\barν_μ)/(ν_e+\barν_e)$ and $\barν/ν$ 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 $E_ν <$ 1 GeV region, which was difficult to assess with the conventional tuning. The flux uncertainty in the $1<E_ν<10$ GeV region was evaluated to be 5\%--7\%, which is an improvement over the conventional tuning.

Figures (14)

• Figure 1: Schematic view of chain interactions associated with neutrino production. The $w_i$ represents a weight for our tuning (Eq. \ref{['eq:weight']}) at the $i$-th vertex.
• Figure 2: Hadron interaction types associated with $\nu_{\mu}$ or $\bar{\nu}_{\mu}$ production (a) and $\nu_{e}$ or $\bar{\nu}_{e}$ production (b). Histograms are normalized by total number of hadron interactions related to neutrino production. Colors show combination of $x_{in}$ and $x_{out}$ of $x_{in} + \textrm{Air} \to x_{out} + X$ interaction. In the red, green, and blue histograms, $x_{in}$ is for the nucleon and $x_{out}$ is for $\pi^{\pm}, K$, and nucleon, respectively. The orange histogram shows collisions where $x_{in} =$ meson. The cyan shows interaction where $x_{in}$ and/or $x_{out}$ are anti-nucleons.
• Figure 3: Momentum distribution of incident particle in hadron interaction associated with $\nu_{\mu}$ or $\bar{\nu}_{\mu}$ production as a function of neutrino momentum. The left, center, and right plots show interactions where outgoing particles are $\pi^\pm, K$, and nucleon, respectively.
• Figure 4: Feynman-X $x_{f}$ distribution of the parent mesons of neutrinos.
• Figure 5: Example of phase-space coverage in $x_{F}$--$p_{T}$ plane. The 2-D histogram shows phase-space of $\pi^{\pm}$ production associated with 0.3--0.5 GeV/$c$$\nu_{\mu}$, where the momentum of incident particle is selected to be $p_{in} = 3$--$5$ GeV/$c$. The regions surrounded by magenta and cyan lines are covered by HARP data with beam momentum = 3 or 5 GeV/$c$.