Monte Carlo simulation

In order to understand the performance of ACC, a Monte Carlo program [52] has been developed to simulate the behavior of Cerenkov photons in the aerogel as realistically as possible. The program consists of two parts: photon transportation inside aerogel tiles and one dimensional amplification in an FM-PMT. All the conceivable effects are taken into account as functions of wavelength. The only unknown factor is the absorption in the aerogel, which is treated as a free parameter and later determined by comparing simulation results with the test beam data.
A Cerenkov photon is transported inside the aerogel radiator according to the photon-transport algorithm developed in the present simulation. The program simulates the output photo-electron yields as accurately as 5 % with only a single parameter. The experimental data of a pulse-height spectrum for single-photoelectron events is well reproduced [50]. The agreement between the simulation and data for the excess noise factor with and without magnetic fields is satisfactory. The incident position dependence of the light yields is also well reproduced by this simulation.
This simulator is implemented in a Belle standard detector simulator based on the GEANT 3. Good performance of pion/kaon separation by ACC has been demonstrated successfully.