The spatial resolution for hit measurement in the TPC is non-trivial, and so, therefore, are the uncertainties which try to estimate the resolution. Hence, the simple question ``What is the spatial resolution?'' cannot be answered simply. Here, and in 6.3, we describe how hit resolutions are determined in the cluster/hitfinder. See [3,6,7,8,9] for further details.
It is believed that such careful evaluation of spatial uncertainties based hit-by-hit on track characteristics represents an improvement over assignment of uncertainty based on signal width and signal:noise alone (perhaps scaled by some ad hoc factor). It is hoped that a corresponding improvement is thus achieved in the track parameters; verification of this improvement is a task for the future.
The parametrizations employed in the cluster/hitfinder are based on simulations with current (1/96) ``standard'' versions of Geant and TPC slow simulator for STAR. Tuning these packages to better reflect reality may require some changes to TCL. These will be reported in future as needed.