# Sampling Off-Axis Neutrino Fluxes with the Short-Baseline Near Detector

## TL;DR

The paper demonstrates how the SBND detector can sample neutrino flux variations with angle to improve physics analyses, including oscillation studies, and provides publicly available flux data and covariance matrices.

## Contribution

It introduces the SBND-PRISM technique to exploit angular flux variations for enhanced neutrino physics measurements and robustness against modeling uncertainties.

## Key findings

- Neutrino flux varies with beam axis angle, enabling angular sampling.
- SBND-PRISM can mitigate uncertainties in cross-section modeling.
- Flux and covariance data are publicly released.

## Abstract

The Short-Baseline Near Detector (SBND), the near detector in the Short-Baseline Neutrino Program at Fermi National Accelerator Laboratory, is located just 110 m from the Booster Neutrino Beam target. Thanks to this close proximity, relative to its 4 m $\times$ 4 m front face, neutrinos enter SBND over a range of angles from $0^{\circ}$ to approximately $1.6^{\circ}$, enabling the detector to sample variations in the neutrino flux as a function of angle-a technique known as PRISM, referred to here as SBND-PRISM. In this paper, we show how muon- and electron-neutrino fluxes vary as a function of the neutrino beam axis angle and how this can be exploited to expand the physics potential of SBND. We make use of a model that predicts an angle-dependent electron-neutrino excess signal to illustrate this effect, such as $\nu_\mu \to \nu_e$ oscillations. We present how SBND-PRISM provides a method to add robustness against uncertainties in cross-section modeling and, more generally, uncertainties that do not depend on the spatial position of neutrino interaction inside the detector. The fluxes, along with their associated covariance matrices, are made publicly available with this publication.