Neutrino Anomalies and Tensions: Experimental Status and Theoretical Interpretations

Abstract

Neutrino oscillations successfully describe flavor conversion across a wide range of experiments, yet the origin of several excesses and deficits remains unresolved. This review connects these observations and long-baseline parameter tensions to their proposed physical explanations, clarifying what remains open and how it can be tested. We examine reactor and gallium measurements, accelerator appearance and disappearance searches, and atmospheric constraints, focusing on sterile neutrinos, non-standard interactions, and decoherence in open-system dynamics. For each mechanism, we assess what it modifies, which observations it can address, and which theoretical assumptions and independent constraints limit its viability. Recent results have restricted several interpretations and weakened some earlier tensions; no single extension provides an uncontested account of all observations. We identify the flavor, baseline, energy, and event-topology signatures needed to distinguish competing explanations and assess whether the remaining anomalies require new physics or reflect unresolved flux, interaction, and detector uncertainties.