Search for a particle with a long interaction length

A search has been carried out for a long-lived particle having an interaction length lambdasub(m) = 300 to 2,000 cm-2 in air. Such a particle, called the mandela, has been proposed by the Leeds group to explain an anomalous energy spectrum of particles observed near sea level with a shallow spectrometer. Data taken at mountain altitude with a deep spectrometer has been examined for compatibility with the existence of the mandela. Although the data tend to favor the mandela hypothesis the results are not conclusive and appear to be explainable by conventional means. (orig.)