Sensitivities of Long and Medium Baseline Experiments to Sterile Neutrinos and Non-Standard Interactions
In this work, we present for the first time, the simultaneous analysis of the non-standard neutrino interactions (NSI) and a light sterile neutrino in the 3+1 framework for the future long- and medium-baseline experiments DUNE and MOMENT, respectively. We show that treating the two sectors separately yields over optimistic sensitivities. The simultaneous presence of sterile-neutrino mixing and complex NSI weakens the $|\varepsilon_{eμ}|$ sensitivity by a factor of $\sim (2-3)$ with the dominant degradation associated with the additional parameter freedom in the flavor-changing NSI sector. DUNE alone fails to achieve $5σ$ CP-violation discovery, once NSI phases are marginalized over. The DUNE+MOMENT combination recovers $>5σ$ sensitivity over a wide range of $δ_{\rm CP}$ space, constrains $\sin^2θ_{24}\lesssim10^{-2}$ and $|\varepsilon_{eμ}|\lesssim0.025$ at $95\%$~C.L., and resolves degeneracies that are intractable for either experiment alone. Our results establish that a multi-baseline strategy combining matter-rich and near-vacuum baselines is necessary for robust parameter extraction in the simultaneous presence of two new physics scenarios. It is also important to perform simultaneous new physics analyses to reliably interpret future precision neutrino oscillation data.