Status of neutrino oscillations II: How to reconcile the LSND result?

TL;DR

This paper analyzes global neutrino oscillation data, including LSND results, and finds that current models struggle to reconcile all experimental evidence, leaving the LSND anomaly unresolved.

Contribution

It evaluates four-neutrino and CPT-violating models against recent data, ruling out certain schemes and highlighting the persistent challenge of explaining LSND.

Findings

(2+2) mass schemes are ruled out at 5.8σ

(3+1) schemes are disfavoured at 3.2σ

CPT violating scenario is disfavoured at 3.4σ

Abstract

We present an analysis of the global neutrino oscillation data including the LSND result in terms of four-neutrino mass schemes and a CPT violating three-neutrino framework. We find that the strong preference of oscillations into active neutrinos implied by recent solar+KamLAND as well as atmospheric neutrino data allows to rule out (2+2) mass schemes at 5.8$\sigma$, whereas (3+1) schemes are disfavoured at the 3.2$\sigma$ level by short-baseline experiments. The CPT violating scenario is disfavoured at 3.4$\sigma$ by KamLAND and atmospheric anti-neutrino data. We conclude that currently no convincing explanation for the LSND signal exists, and it remains a puzzle how to reconcile it with the other evidences for neutrino oscillations.