<span><strong>Characterizing cosmic muon flux as a function of zenith angle using geiger-müller coincidence setup</strong></span>

The study uses a low-cost, dual Geiger-Müller (GM) tubes coincidence detection device in an outdoor environment to evaluate the relationship between cosmic muon flux on zenith angle. Coincidence occurrences decreased from 484 counts at vertical alignment to 47 counts at horizontal alignment, with zenith angles of 0°, 30°, 45°, 60°, and 90°. Under normal values at sea level, the measured directional muon flux at 0° was 1.301 muons/cm²/min. An exponent of n = 1.063 ± 0.107 was obtained by fitting the angular dependency to a cosine power law via a Bayesian Markov Chain Monte Carlo (MCMC) approach. The result indicates a qualitative agreement with a cosine-based angular distribution under practical constraints, despite the fact that this value is less than the theoretical expectation (n ≈ 2). The setup achieved a Noise Rejection Ratio (NRR) of 0.373% and a Directional Index (DI) of 0.804, indicating moderate directional selectivity and noise suppression. This study demonstrates the viability of Geiger-Müller detectors in basic cosmic ray research and educational contexts.