The accuracy (left panel) and purity (bottom right panel) of the charge determination as a function of Z. We define the accuracy as the fraction of correctly identified events for a given Z_mc and the purity as the fraction of events in a Z_rec class for which Z_rec = Z_mc. The top right panel shows the standard deviation, σ_Z, of the reconstructed-charge distributions (the columns in Fig. 7). The blue curves show the performance for an exact identification of the charge (∆Z = Z_rec−Z_mc = 0). The yellow and red curves illustrate the improvement when we allow |∆Z| ≤ 1 and |∆Z| ≤ 2, respectively. The insets in the lower panels provide zoomed-in views for Z ≤ 8.