A Search for Long-Lived Charged Particles in Cosmic Rays

A search for a new long-lived elementary particle produced in cosmic ray air showers is presented. This measurement is based on data recorded from November 2009 to December 2010 in a plastic scintillation detector developed and housed at the University of Illinois at Chicago. No evidence of a new particle was observed in the decay spectrum of stopped charged particles. A 95% confidence level upper limits of production over a broad range of lifetime hypotheses from 5μs to 0.3s, are given relative to the observed muon decay rate. In the most sensitive region around a lifetime of 30μs, new particle production is excluded above 0.0002 of the stopping muon decay rate.