History of "Anomalous" Atmospheric Neutrino Events: A First Person Account

TL;DR

This paper recounts the discovery and historical development of the atmospheric neutrino anomaly, a key piece of evidence supporting the modern understanding of neutrino oscillations and mass.

Contribution

It provides a first-person historical account of the discovery and scientific context of the atmospheric neutrino anomaly over 40 years.

Findings

Observation of reduced high-energy muon neutrinos from the atmosphere

Historical account of the anomaly's discovery in the 1980s

Contextual analysis of the scientific motivations of the era

Abstract

The modern picture of the neutrino as a multiple mass highly mixed neutral particle has emerged over 40 years of study. Best known of the issues leading to this picture was the apparent loss of neutrinos coming from the sun. This article describes another piece of evidence that supports the picture; the substantial reduction of high energy muon type neutrinos observed in nature. For much of the 40 year period, before the modern picture emerged this observation was known as the "atmospheric neutrino anomaly", since as will be seen, these neutrinos originate in the Earth's atmosphere. This paper describes the discovery of the atmospheric neutrino anomaly. We explore the scientific context and motivations in the late 1970's from which this work emerged. The gradual awareness that the observations of atmospheric neutrinos were not as expected took place in the 1983-1986 period.