The STAR-TPC cluster/hitfinder is a software package, implemented in the TPC Analysis Shell (TAS) as the TCL package, designed to extract from the raw data pad-row crossing positions (``hits'') for charged particles that traverse the active volume of the TPC. The cluster/hitfinder is the first offline analysis (non-calibration) software that will process the TPC data in the current model of data reduction; almost all other offline software, including physics analysis software, build on the output of the cluster/hitfinder. Therefore, it is important that the general workings of this first software package are understood.
Our current model of data reduction, in which one first finds hits, and then does tracking on these hits, corresponds to the standard method used by most TPC groups. Of course, other models may be envisioned; for example, one may want to try tracking with the pixel information alone. These alternative avenues should be pursued and the results compared with the standard model.
The relationship of the TCL package and its associated input and output structures (tables) to other low-level simulation and reconstruction software is shown in Figure 1. Two analysis modules, TCL and TPH, perform the clusterfinding and hitfinding, respectively.
Figure 1: Relationship of low-level software modules.