Software aspects of the NA59 experiment

The NA59 experiment on the CERN SPS-H2 beam-line took data during the summers of 1999 and 2000, to investigate the creation of circularly polarized photons starting from unpolarized electrons. The computational hub for the experiment was Northwestern University, where two clusters of computers served for the Monte Carlo simulation of the experiment, the production of the data summary tapes, and the offline data analysis. After reconstructing about half a million e **+e**- pairs and comparing the results with the theoretical predictions, our experiment was first to show the birefringence property of the crystals for the photons in the 30-170 GeV range. This paper presents the newly developed methods in the event reconstruction and offline data analysis. 12 Refs.