THEMI - Monte Carlo Generation of Electromagnetic Events
Dennis Blanchard, US Atomic Energy Commission (AEC), USDOE, William P. Swanson · 1970
In designing or analyzing experiments at high-energy electron accelerators, it is often useful to be able to simulate the effects of the dominant interactions of photons in a realistic way. For example, in an experiment designed to study these interactions, a simulation by Monte-Carlo is useful in choosing design parameters. In other experiments, where these interactions may constitute a severe background; this background may be made manageable by Monte-Carlo studies. For this purpose, a set of FORTRAN subroutines, .THEMI, has been written, which provides (a) total cross sections for hydrogen and (b) random "events" whose kinematics are distributed according to theoretical models which have been essentially confirmed by numerous experiments. The usefulness of this set of routines is illustrated by its application in a real experiment. The experiment is a photoproduction experiment using the SLAC 2-M streamer chamber. The target is a 1/2-inch-diameter thin-walled tube filled with hydrogen gas, and a well-collimated photon beam is introduced along the axis of the tube. Vertices of events are invisible within this tube. Four distinct but related questions have been investigated.