Some formulae for estimating tracking errors

Universal curves and approximate formulae for the track parameter error matrix form the optimal fit are derived for homogeneous tracking detectors in the continuous measurement limit. Formulae for estimating the track parameter error matrix resulting from diagonal uniformily weighted fits have been published in many places. This note derives similar formulae for optimal fits. It also demonstrates that in the limit of continuous measurement, the matrix elements are described by universal curves. The case treated is heterogeneous systems of many layers. In general heterogeneous systems require numerical calculation