Track reconstruction efficiency was estimated using high quality tracks, defined as those that are produced at the primary vertex and generate at least 20 space points in the TPC. The reconstruction efficiency is defined as the fraction of those good quality tracks that are found by the pattern recognition program and that more than 90% of the space points assigned to the track were generated by it.
Figure 1 shows the track reconstruction efficiency as a function of transverse momentum, , for the five configurations considered with and without vertex constraint. As can be expected, the efficiency deteriorates when the number of pad-rows decreases.
Figure 2 shows the the track reconstruction efficiency as a function of rapidity, , for the various configurations.
Figure 3 shows the momentum resolution as a function of transverse obtained with the various pad-row configurations for central Lund AuAu events. The momentum resolution was obtained by fitting a gaussian to the relative difference between the real and the measured momentum in the various intervals. As can be observed, the resolution obtained when only pad-rows 21-45 or 30-45 are used without vertex constraint is rather poor. The rest of the distributions look rather similar, especially for the full TPC with even and third pad-rows. Table 7 contains the momentum resolution integrated over .
The momentum resolution as a function of in a larger range in transverse momentum is shown in Figure 4. The results shown were obtained from a sample of events with tracks generated with a flat distribution in the range 0-40 GeV. The momentum resolution was obtained from the comparison of reconstructed and generated momenta. The dispersion of the distributions, rather that a gaussian fit, was taken as the momentum resolution, since some distributions are not gaussian. In this case the results corresponding to pad-rows 21-45 and 30-45 without vertex constraint were not plotted since they are very poor. The other configurations yield rather similar results.