A critical appraisal of the LSND anomaly

TL;DR

This paper critically examines the LSND anomaly, questioning its interpretation by analyzing background predictions and experimental data, and discusses the inconsistency with MiniBooNE results to clarify the anomaly's origin.

Contribution

It provides a detailed critical assessment of the LSND anomaly, focusing on background flux predictions and experimental data analysis to clarify its origins.

Findings

Background anti-nu_e flux predictions are uncertain.

MiniBooNE results conflict with LSND interpretation.

Pion spectra measurements are crucial for background estimation.

Abstract

The so-called 'LSND anomaly', a 3.8 sigma excess of anti-nu_e events interpreted as originating from anti-nu_mu -> anti-nu_e oscillation, gave rise to many theoretical speculations. The MiniBooNE Collaboration reported inconsistency of this interpretation with the findings from their search for nu_mu -> nu_e oscillations. Yet the origin of the LSND anomaly was never clarified. A critical issue is the prediction of the background anti-nu_e flux that was used in the analysis of the LSND experiment. For this, decisive input comes from pion spectra measured with the HARP large-angle spectrometer under conditions that closely resemble the LSND situation: a proton beam with 800 MeV kinetic energy hitting a water target.