P326 Software Architecture

The incredible suppression of backgrounds (12 orders of magnitude) required for the measurement of K+ rarr pi+ nunu^- decays with a 10% accuracy and a signal/noise ratio of 10:1, calls for very detailed description and simulation of the performances of all the detector elements of the experiment. Moreover, in the design phase, it is crucial to have a precise Monte Carlo, for the optimization of the geometry with respect to the performances, the costs and the material budget. Many different pieces of code, specialized for the different detectors and developed by different groups using different flavours of standard simulation packages, should be assembled in order to produce a reliable and complete MC production. A trigger simulation and a realistic event reconstruction are also mandatory in order to perform useful physics studies on signal and background MC samples. The P326 software architecture has been designed in order to have at the same time a complete and reliable simulation and a well optimized code (both for CPU and disk demands). A Virtual Monte Carlo package from ROOT is extensively used to provide the integration of GEANT3 and GEANT4 existing simulation codes (very specialized and optimized) in a common framework, using a common description tool and implementing a general Event Data Model. The common description/visualization and digitization/storage tools are based on ROOT. This architecture is in an advanced stage of development and MC dedicated productions are due starting by the end of year 2006.