RadPhi TechNote
radphi-2001-101
January 11, 2001
The polar angle of a photon from the Radphi target producing a shower in the lead-glass detector (LGD) depends upon all three coordinates (x,y,z) of the shower centroid in the LGD. In the coordinate system with its origin in the center of the target and its z-axis pointing along the incident beam direction, only x and y are directly determined from the data while z has to be inferred from the shower energy. In this note a combination of shower simulations and phenomenology is used to motivate a recommended way of calculating the z of a shower. This result is compared with the method that is found in the code that has been in use up to the time this note was written.