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Introduction
MultiFit has been developed within the scope of the diploma thesis of M.E. Janssen. Its main task is to reconstruct particle tracks from measured charge signals and to calculate the values that are needed in the analysis of the detector performance. The software package has been designed to be adjustable to different prototype layouts and to be able to reconstruct multiple tracks in one event. Furthermore is provides detailed output on the reconstruction to have the possibility to analyze the effects and systematics of the reconstruction process and the detector.
MultiFit is written in C++ and makes use of the ROOT and LCIO frameworks. The data input formats are the ROOT and LCIO based data formats, the output is written in the ROOT format. The reconstruction is implemented as a three step process and the intermediate results are written to separate files after each reconstruction step (see Figure 1):
The coordinate system used for the calculations in MultiFit is shown in Figure 2. It's a right-handed coordinate system, where the Z axis runs along the drift direction of the electrons in the TPC, the X axis runs parallel to the pad rows and the Y axis perpendicular to them. The origin of this coordinate system lies in the top left corner of the pad plane.
The different steering parameters needed for the reconstruction are given to MultiFit in a configuration file. To be able to monitor the reconstruction process and to examine single events, MultiFit provides the possibility to switch on a graphical display which shows the process event-wise in a window on the screen and gives the possibility to save screenshots.
In the following, the three steps of the reconstruction process will be described.
