Monte Carlo studies on the response of the TRACER cosmic ray detector

TRACER (Transition Radiation Array for Cosmic Energetic Radiation) is a large area balloon-borne detector for the determination of the energy spectra of heavy cosmic ray nuclei ($8\le Z \le 26$) in the energy range from $\sim 500$ MeV/nucleon up to $\sim 10$ TeV/nucleon. The key component of TRACER is an array of 1600 single wire proportional tubes. The tube array provides the trajectory of the particle and also the Lorentz factor from the measurement of specific ionization loss (dE/dx) and transition radiation. The trajectory reconstruction procedure is complex and Monte Carlo studies are essential for the development of the algorithm. A full Monte Carlo simulation has been developed for TRACER using GEANT4. In addition to track reconstruction the simulation investigates important instrument characteristics such as geometric aperture, intrinsic resolution, $\delta$-ray contribution to the signals, calibration of energy measurements, deconvolution of energy spectra and determination of particle fluxes. We shall describe in detail the Monte Carlo studies and compare them to data obtained during a long duration balloon flight in 2003.