Issue with angular distribution


I am currently plotting the angular distribution for secondary particles but i seem to only be getting one side of them. I am expecting a gaussian distribution but it only seems to be plotting half of the distribution? Does anyone know why this would be happening?


In spherical coordinates in G4 (see CLHEP/Vector/ThreeVector.h), v.theta() is the angle with respect to the +Z axis, and runs from 0 to pi. v.phi() is the azimuthal angle around Z. If you’re plotting v.theta(), you’ll never see a negative value.