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arXiv · 2603.27681

Absence of Quadratic-Order Sensitivity to Small Neutrino Mass Splittings in Disappearance Measurements

Sanjeev Kumar Verma
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Abstract

Neutrino disappearance measurements using binned reconstructed-energy spectra exhibit a regime in which small mass-squared splittings become unidentifiable at quadratic order when smooth spectral shape uncertainties are represented by profiled nuisance parameters in the fit. In the small-phase limit, the oscillation-induced modification of the detected spectrum is quadratic in the mass-squared splitting and produces a smooth deformation of the reconstructed-energy distribution. If the nuisance deformation functions used in the fit can reproduce this energy dependence across the fitted bins, the quadratic oscillation-induced distortion can be absorbed by the systematic deformation space and the profiled chi-squared remains unchanged at this order. Sensitivity to the mass-squared splitting then arises only from higher-order oscillation effects or from restrictions imposed on the allowed smooth spectral freedom.

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Sanjeev Kumar Verma. 2026-03-29. Absence of Quadratic-Order Sensitivity to Small Neutrino Mass Splittings in Disappearance Measurements. https://arxiv.org/abs/2603.27681

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