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Spacial Distribution of muons in Air Showers

A Large Array experiment consisting of 24 scintillation counters was commissioned in order to measure the number of muons in cosmic rays at the Earth's surface. Six separate DAQ streams were required since each QuarkNet DAQ card has a maximum of 4 input channels. DAQ and detectors were gathered from many schools and brought to UIC during our 2006 workshop. Data was collected for 3 weeks, however only a 2-hr period was analyzed using UIC code, followed by hand scanning and building of 20-detector events from separated data streams that fired at the same time. One set of detectors were commissioned with too low HV and were therefore inefficient for detecting muons.

Our plan is to correlate the 6 separate streams for the entire data set, but the muon multiplicity extracted from a 2-hr data sample is shown. Corrections have been applied for the trigger bias, which is complex. One of our graduating QuarkNet high school students wrote a program during his first semester in college, to estimate the true number of hits, given the number observed, under the assumption that all detectors were efficient at detecting muons at the same rate, by modeling the affect of triggering requirements (at least 2 hits per 4-counter array). For example, our 20-counter detector would trigger and record data with 4 hit counters, where 2 counters hit array A and 2 counters hit array B, but would not record events where 3 counters hit A and 1 counter hit array B, because the B array trigger would not have been satisfied.

The number of times N of the 16 counters were hit simultaneously, is presented as a function of N (blue diamonds). It is compared with data from an earlier test in the Barn at Fermilab (circles). The fairly flat distribution at high multiplicity demonstrates that some cosmic ray air showers contain many muons.
dense multiplicity