Scintillator–SiPM Detection of Cosmic-Ray Muons: Physics, Detector Architectures, Coincidence Techniques, Acceptance, and the Comparability of Reported Flux and Angular Measurements

Plastic scintillators read out by silicon photomultipliers (SiPMs) are now widely used in compact cosmic-ray muon telescopes, from desktop counters to square-metre muography hodoscopes. The measurements these instruments report, however, are difficult to compare: vertical intensity, integral flux, coincidence rate, and acceptance are not always distinguished, and the quantities that control them — geometric acceptance, plane efficiency, coincidence window, energy threshold, and environmental conditions — are reported inconsistently. This review is organized around that measurement chain rather than around individual instruments. It summarizes the muon physics that fixes what a surface telescope can measure, treats the scintillator and SiPM properties that set the photoelectron budget and the singles rate, classifies published detector architectures, and analyses coincidence background, acceptance, and efficiency quantitatively. Published zenith-angle exponents are then compared: acceptance-corrected tracking and pulse-charge measurements give n = 2.00 ± 0.04 (stat) ± 0.14 (syst) and 1.90 ± 0.06 (stat) ± 0.10 (syst), whereas tilt scans of wide-acceptance counting telescopes fitted directly with a cosine-power law give 1.39 ± 0.01 and 1.44 ± 0.06. A numerical acceptance calculation performed for this review, and clearly separated from literature-derived values, shows that for two square planes of width a separated by d the apparent exponent obtained from uncorrected tilt-scan rates falls from 1.99 at d/a = 10 to 1.62 at d/a = 1 and 1.28 at d/a = 0.5 when the true exponent is 2, and that forward folding the same model through the acceptance recovers the input exponent exactly. Finite acceptance can therefore account for a substantial fraction of the published spread without invoking atmospheric physics, although the geometries of the published telescopes differ from the idealization used here and no correction is derived for them. The review closes with an uncertainty framework, a minimum-reporting checklist, and an assessment of the gaps that currently limit the comparability and the imaging performance of scintillator–SiPM muon detectors.

cosmic-ray muons, plastic scintillator, silicon photomultiplier, coincidence counting, geometric acceptance, zenith-angle distribution, muography

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