I tried calculating the efficiency from the Run 9 dijet embedding sample using the following algorithm:

1. Loop over MC tracks.  If 'IdVx == 1' (i.e. its vertex is the primary interaction vertex), |eta| < 1, and is neutral, fill a histogram with its pT and perform steps 2 and 3. Otherwise skip track.
2. Loop over primary tracks.  If 'IdTruth == IdMc' (where 'IdMc' is the track ID of the MC track), then fill a histogram with the pT of the MC track in question.
3. Apply QA cuts to primary track.  If it passes them, fill a histogram with the pT of the MC track in question.

MC track refers to the generator (Pythia) level tracks stored in the 'StMuMcTrack' branch of the MuDst's.  The plots below were made using only the RFF, pTparton = (9, 11) GeV/c files from the Run 9 dijet sample.