Search

An increased data sample of identified secondary muons is collected at detection level. Project GRAND identifies secondary cosmic ray muons from electrons utilizing a thin steel absorber and tracking (PWC) chambers. The resulting angular resolution for the primary is about +/- 5 degrees. Since there is a 1.5% probability that a 100 GeV gamma primary will produce a single muon track at ground level, the high statistics allows a search for angular enhancements due to gammas. More than 100 billion muons are identified and analyzed. A table of stellar sources is examined., Comment: 4 pgs; includes 1 fig. and 2 tables. HE.3.2.10 in 26th ICRC, 2, 104, (1999)

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., Comment: 4 pages

Project GRAND presents the results of a search for coincident high-energy gamma ray events in the direction and at the time of nine Gamma Ray Bursts (GRBs) detected by BATSE. A gamma ray has a non-negligible hadron production cross section; for each gamma ray of energy of 100 GeV, there are 0.015 muons which reach detection level (Fasso & Poirier, 1999). These muons are identified and their angles are measured in stations of eight planes of proportional wire chambers (PWCs). A 50 mm steel plate above the bottom pair of planes is used to distinguish muons from electrons. The mean angular resolution is 0.26 degrees over a +/- 61 degree range in the XZ and YZ planes. The BATSE GRB catalogue is examined for bursts which are near zenith for Project GRAND. The geometrical acceptance is calculated for each of these events. The product is then taken of the GRB flux and GRAND's geometrical acceptance. The nine sources with the best combination of detection efficiency and BATSE's intensity are selected to be examined in the data. The most significant detection of these nine sources is at a statistical significance of +3.7 sigma; this is also the GRB with the highest product of GRB flux and geometrical acceptance., Comment: 4 pages. Superseded by astro-ph/0004379

Project GRAND presents results on the atomic composition of primary cosmic rays. This is accomplished by determining the average height of primary particles that cause extensive air showers detected by Project GRAND. Particles with a larger cross sectional area, such as iron nuclei, are likely to start an extensive air shower higher in the atmosphere whereas protons, with a smaller cross section, would pass through more air before interacting and thus start showers at lower heights. Such heights can be determined by extrapolating identified muon tracks backward (upward) to determine their height of origin (Gress et al., 1997). Since muons are from the top, hadronic part of the shower, they are a good estimator for the beginning of the shower. The data for this study were taken during the previous year with 20 million shower events., Comment: 4 pages including 1 table and 4 figures. OG.3.1.12 in 26th ICRC, 4, 172 (1999)

Project GRAND is an extensive air shower array utilizing position sensitive detectors of proportional wire chambers. The 64 detectors deployed in a field 100 m x 100 m are located at 86.2 deg W and 41.7 deg N, at 220 m above sea level. The project was completed about two years ago and has been taking data, simultaneously on two triggers: 1) multiple-hit coincidence triggers which collect data on extensive air showers, and 2) 200 Hz triggers which collect the single tracks stored in each station during the last 5 msec., Comment: 4 pages, 4 figures. Appeared in 26th ICRC, vol 5, 304 (1999), OG.4.4.02

Project GRAND preents a map in right ascension and declination for single cosmic secondary tracks which have been identified as muons. These muons are measured in stations of proportional wire chambers (PWCs) which have a mean angular resolution of 0.26 deg. A 50 mm steel plate interspersed with the PWCs is used to distinguish muons from electrons. Two years of data are accumulated in a map of right ascension and declination which covers all of the northern hemisphere and a small portion of the southern hemisphere. The total number of muon tracks in this data sample are 40 billion. Significant large angular structure is found in this map; the deviations from average are small compared to the average, but because of the high statistics, the deviations from average are statistically significant to many standard deviations. Systematic effects in the data are minimized by averaging over this two year period. These results are similar to those obtained in previous data., Comment: 4 pages, 3 figures

Project GRAND measures the asymmetries of secondary cosmic muons by calculating the differences between the muons from the east and the muons from the west for complete solar days. A similar north-south difference is also presented. These muons are identified in single track data taken with the 64 stations of Project GRAND; the data cover a two year span with a total muon sample of 30 billion muons., Comment: 4 pages, 2 figures