Zenith angle dependence of pressure effect in GRAPES-3 muon telescope

A large area (560 m^2) muon telescope in the GRAPES-3 experiment at Ooty, India records muon intensity at high cutoff rigidities (Rc) varies from 14–32 GV along 169 independent directions spanning a field of view of 2.3 sr. The threshold energy of the recorded muons is sec(theta) GeV along a direction with a zenith angle (theta) and with the average angular accuracy of∼4 degrees. The directional capabilities of the muon telescope are exploited for studying the effect of atmospheric pressure on the muon flux as a function of Rc. It is observed that the barometric coefficient relationship with logarithmic Rc can be well described by a second order polynomial function with a high Spearman Rank correlation coefficient of 0.99