My first project with the CERN ATLAS Group was a training exercise to build my own Monte Carlo simulation.  The Monte Carlo simulation is built on the assumption that a highly energetic particle will decay into two particles.  The first particle will scatter by an angle theta and an angle phi relative to the initial trajectory of the parent particle.  The angles are governed by probability distributions p(theta)=1/(1+theta) and p(phi)=1/(1+ phi).  Each angle is determined stochastically.  The first particle will then have an energy which is a fraction z of the initial energy E.  From these values we can determine the trajectory of the second particle based on relativistic energy and momentum conservation.  The first and second particles then decay in the same manner.  The simulation assumes that once a particle reaches an energy Ecrit, it will no longer decay.  This value is initially determined in the simulation.

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