Measuring the Energy Distribution of Cosmic Ray Muons Using a Cerenkov Detector

Mitchell Ambrose and Aaron Jawson

University of Minnesota

Methods of Experimental Physics Spring 2012

Abstract

To determine the shape of a portion of the cosmic ray muon energy distribution, we constructed a threshold Cerenkov detector sensitive to muons with energies between 1 and 5 GeV. After measuring the integral muon intensity at nitrogen pressures between 1 and 10 atm, the data was fit based on a diffusion model of muon production by pions in the Earth?s atmosphere which describes the integral energy distribution as a power law with exponent -1. The best fit value for the was calculated to be 2.77 +/- 0.20, which is 0.25 sigma higher than the value obtained by B.C. Rastin (2.72 +/- 0.01). Although the accuracy of our result was greatly limited by our device?s low muon detection efficiency, we contend that the effectiveness of our detector design could be significantly improved with a few minor design adjustments, and thus we conclude that it is feasible to use a threshold Cerenkov detector to accurately measure the shape of the cosmic ray muon energy distribution.