The role of final-state interaction modeling in neutrino energy reconstruction and oscillation measurements

TL;DR

This paper demonstrates that uncertainties in modeling final-state interactions can significantly distort neutrino energy spectra, potentially mimicking oscillation effects and impacting measurements in next-generation experiments.

Contribution

It highlights the critical need for improved FSI modeling and dedicated measurements to reduce uncertainties in neutrino oscillation analyses.

Findings

FSI modeling variations can alter reconstructed neutrino spectra significantly.

Distortions from FSI can mimic changes in oscillation parameters.

Improved FSI characterization is essential for robust neutrino measurements.

Abstract

We present a quantitative demonstration that, without additional theoretical and experimental efforts, realistic variations in final-state-interaction (FSI) modeling may alter reconstructed neutrino-energy spectra at next-generation long-baseline experiments by amounts comparable to, or larger than, variations induced by oscillation-parameter shifts at their projected precision. Using the DUNE flux and baseline as a case study, we show that these FSI-driven distortions can mimic the effects of changes in the oscillation parameters $\Delta m^2_{32}$ or $\delta_{\rm CP}$, producing a potential degeneracy. Our analysis thereby underscores the urgent need for an improved characterisation of FSI to enable robust constraints from near detectors through the development of theory-driven uncertainty parameterisations benchmarked with dedicated new measurements.