Track-by-track analysis of Victor's proposed changes

Same dataset and methodology as in other recent studies (e.g. 1,2).

I. Victor's changes to Sti vs. DEV:

• 25 out of 131k (0.02%) matched tracks have differences in hits (and consequently tiny differences in track parameters; more lose hits than gain, ranging from [-7,+1] except for one with +5, see Fig. 1)
• 17 unmatched from DEV
• 7 unmatched from Victor
• No obvious phase space biases for unmatched or modified tracks other than low number of hits
• Victor's appears to run ~4% faster (see Fig. 2)

Fig. 1: Δ(N_hits) for modified matched tracks
Fig: 2: ratio of event reconstruction times for Victor / DEV



II. Victor's changes to StiCA vs. DEV:

• 884 out of 154k (0.6%) matched tracks have differences in track parameters; larger fraction of low-p_T tracks (3%) affected than high-p_T tracks (0.1%) (low-p_T means large magnitude for q/p_T as plotted, see Fig. 3)
• Modified tracks have negligible mean change in q/p_T and DCA, with spreads of up to ~1 MeV/c and 100 μm respectively at low p_T (see Figs. 5 & 6)
• 48 unmatched from DEV
• 21 unmatched from Victor
• No obvious phase space biases for unmatched tracks other than low number of hits
• Victor's appears to run ~4% slower (see Fig. 7)

Fig. 3: Δ(N_hits) for modified matched tracks
Fig. 4: fraction of tracks modifed vs. q/p_T for matched tracks
Fig. 5: Δ(q/p_T) vs. q/p_T for matched tracks
Fig. 6: Δ(DCA) vs. q/p_T for matched tracks
Fig. 7: ratio of event reconstruction times for Victor / DEV





III. Victor's bug fix to StiCA vs. Victor's StiCA

• Nearly all matched tracks (129k) are modified
• On average, 0.05 hits lost per track
• On average, ~1.5 MeV/c in p_T gained per track, with an odd p_T dependence (see Figs. 8 & 9)
• 26k unmatched from Victor's StiCA
• 28k unmatched from Victor's bug-fixed StiCA
• Unmatched fractions higher at large DCA (~30% at DCA of ~2cm!), low p_T, and low number of hits
• Bug-fixed appears to run ~8% faster (see Fig. 10)

Fig. 8: Δ(q/p_T) vs. q/p_T for matched tracks
Fig. 9: Δ(p_T) vs. q*p_T for matched tracks
Fig. 10: ~ratio of event reconstruction times for fixed / unfixed


-Gene