Gene has identified You do not have access to view this node which are not being reconstructed by Stv.  This class of tracks generally has its first and last point on the same side of the TPC, and is contained between the z-vertex and the central membrane.  In order to investigate this further, I generate a sample of muons thrown into the phase space where Gene finds events missing.  I cannot reproduce the inefficiency seen in the AuAu minbias event sample which Gene observes.

Event sample:

• 1000 events
• 1 muon per event
• 0.1 < pT < 10.1 GeV
• η = 0.5, 0 < φ < 2π
• z vertex = -200.0 cm, width = 0

Figure 1 -- Track psuedorapidity vs first point on track.  942 / 1000 events reconstructed in simple sample at left.  At right, Gene's plot using the AuAu minbias sample.  NOTE: Scales are different.

Figure 2 -- Last point vs first point.  Simple MC left, Gene's plot using AuAu minbias sample right.  Scales are the same on this one.

Conclusions:  ???