subject : Use StMiniMcTree from the bfc chain (mixed D0/D0bar + hijing, or single D0 ) to look at the differences btw true D0's and all other pairs (fake)

In particular, we want to look at the DCA of tracks to PV  for true D0's and for fakes.

1. true D0 are selected with :

• geant_id (track1)=8 and geant_id (track2) =12
• parentgeant_id (track1)=37 and parentgeant_id (track2) =37
• parentKey (track1) = parentKey (track2)

Some initial plots are here 

• update (5/15)

Use the completed sample of Joe to make dca vs. InvPt plots

Fig1 : dcaXYGl vs 1/PtGl

from this plot, I used FitSlices to get the rms and mean

Fig2 : resolution vs 1/PtGl

Fig3 : same as Fig2 but zoomed

Fig4 : mean DCA vs 1/PtGl

Fig5 : pT distribution of true D0's and fake

•  minimc files also filled the reconstructed, the primary and the MC version of kinematics variables (pt, dca,eta ...)

For example  :

 Float_t         mMatchedPairs_mDcaXYPr[kMaxmMatchedPairs];   //[mMatchedPairs_]

 Float_t         mMatchedPairs_mDcaZPr[kMaxmMatchedPairs];   //[mMatchedPairs_]

 Float_t         mMatchedPairs_mDcaXYPrMcV[kMaxmMatchedPairs];   //[mMatchedPairs_]

 Float_t         mMatchedPairs_mDcaZPrMcV[kMaxmMatchedPairs];   //[mMatchedPairs_]

which refers to :

StMiniMcMaker/StMiniMcMaker.cxx:  tinyRcTrack->setDcaXYGl(computeXY(mRcVertexPos,glTrack));

StMiniMcMaker/StMiniMcMaker.cxx:  tinyRcTrack->setDcaXYGlMcV(computeXY(mMcVertexPos,glTrack));

so dcaXYGl (dcaXYGlMcv) is the dca in XY with respect the reco. (MC) vertex

Fig 6 : dcaXYGlMcV vs 1/PtMc 

Fig 7 : resolution vs 1/PtMc

comments : there is no obvious difference between the reco and MC branch

• same dca resolution plots but for the Z component

Fig8 : resolution (Z) vs 1/PtMc

 Fig9 : comparison of dca resolution (XY) vs 1/PtGl for flat pt D0 and powerlaw pt, random vertex

black : dca resolution of pion from true D0 (in the 5D0/D0bar + hijing sample, power lat pt D0)

red : dca resolution of pion from fake D0 (in the 5D0/D0bar + hijing sample, power law pt D0)

blue : dca resolution of pion from true single D0 (flat pt)

9/25 : note  on the umber of hits on minimc

tinyRcTrack->setFitPts(glTrack->fitTraits().numberOfFitPoints(kTpcId));
tinyRcTrack->setFitSvt(glTrack->fitTraits().numberOfFitPoints(kSvtId));
tinyRcTrack->setFitSsd(glTrack->fitTraits().numberOfFitPoints(kSsdId));