Dr Jonathan Lister: We do get upward directed muons their source being radioactivity from soil, rocks and building materials and once the gamma rays enter the scintillator they interact with the atoms creating muons etc. He maybe should have stated that muons from cosmic sources are headed downwards. Lead shielding under the detectors, about 5cm, will stop these gamma rays but paradoxically too thin a lead shield actually increases the upward counts.
Andrew: Can I assume that these numbers don’t meaningfully affect the counts on the muon detectors in coincidence?
Dr Jonathan Lister: The count from the radioactivity as the background count which will be a constant factor whereas the cosmic muon showers are dependent on CMEs, Sunspot activity, location on the globe, local height above sea level etc.
Andrew: Are the detection rates at LRO of roughly 0.120 counts/second in coincidence mode the rates expected?
Dr Axani: The master detector should see roughly 1.2+/-0.3 Hz, and the coincidence detector rate depends on how you have them setup. If the detectors are setup such that the two scintillator slabs are touching, the coincidence rate should be ~0.4Hz. If they are in their respective cases, sitting one-on-top another, the rate should be roughly 0.15 (if my memory is correct). The longitudinal/latitude effect only causes percent level changes at sea level. [And about LRO’s Muon Detector setup:] Looks good! Those rates look about right.