Revisiting the 'LSND anomaly' I: impact of new data

TL;DR

This paper reevaluates the LSND anomaly by incorporating new and historical pion production data, which increases background estimates and reduces the anomaly's statistical significance from 3.8σ to 2.9σ, challenging its interpretation as evidence for sterile neutrinos.

Contribution

It provides updated background estimates for the LSND experiment using new pion production data, questioning the anomaly’s significance and its implications for sterile neutrino models.

Findings

Background estimates increased, reducing anomaly significance.

Anomaly significance decreased from 3.8σ to 2.9σ.

Further analysis will question LSND data interpretation.

Abstract

This paper, together with a subsequent paper, questions the so-called 'LSND anomaly': a 3.8 {\sigma} excess of anti-electronneutrino interactions over standard backgrounds, observed by the LSND Collaboration in a beam dump experiment with 800 MeV protons. That excess has been interpreted as evidence for the anti-muonneutrino{\to} anti-electronneutrino oscillation in the {\Delta}m2 range from 0.2 eV2 to 2 eV2. Such a {\Delta}m2 range is incompatible with the widely accepted model of oscillations between three light neutrino species and would require the existence of at least one light 'sterile' neutrino. In this paper, new data on pion production by protons on nuclei are presented, and four decades old data on pion production by neutrons on nuclei are recalled, that together increase significantly the estimates of standard backgrounds in the LSND experiment, and decrease the significance of the 'LSND anomaly' from 3.8 {\sigma} to 2.9 {\sigma}. In a subsequent paper, in addition the LSND Collaboration's data analysis will be questioned, rendering a further reduction of the significance of the 'LSND anomaly'.