Can EGRET's Gamma Ray Sources > 100 MeV Be Seen with Single Secondary Cosmic Muons from Gammas > 30 GeV?

Abstract

The high energy gamma ray sources provided by experiment EGRET on the Compton Gamma Ray Observatory are examined, testing Project GRAND's ability to detect primary gamma rays by means of studying secondary muons. There is ~1.5% chance that a 100 GeV primary cosmic gamma ray will produce a muon at detection level (Fasso & Poirier, 1999), a probability which increases with increasing gamma energy. Project GRAND has 80 square meters of muon detector which identifies secondary muons >0.1 GeV and measures their angles to 0.26 deg (projected angle in the XZ and YZ planes). Data taken during the last two years are analyzed. A table of EGRET's gamma ray sources is examined (The Third EGRET Catalog of High Energy Gamma Ray Sources (EGRET webpage, 1999). EGRET's flux (>0.1 GeV), angular information, and spectral index were extrapolated to GRAND's energy region (>30 GeV). Then the geometrical acceptance was calculated for each of these events. Thus, GRAND's sensitivity to each of EGRET's sources was predicted. A product of extrapolated flux and GRAND's detection sensitivity yields an overall parameter indicating GRAND's relative sensitivity to each source, assuming an energy dependence given by EGRET's spectral index. The 14 sources with the best extrapolated detection efficiency were selected to be examined with the data.