Using new ACD merit variables in background rejection
Current background rejection
Prefilters:
Cut |
Purpose |
Gamma Effic |
Bkg Effic |
Expression |
---|---|---|---|---|
BasicTileCut |
Reject events with track pointing at struck tile: |
95.1% |
8.1% |
Tkr1SSDVeto == 0 && AcdTkr1ActiveDist > -16 && AcdTkr1ActDistTileEnergy > .4 |
RibbonCut |
Reject events with track pointing at struck ribbon |
94.9% |
7.7% |
(AcdRibbonActDist > -(2 +350/sqrt(max(20,CTBBestEnergy))) && Tkr1SSDVeto < 3 && AcdRibbonEnergy > .05 ) |
TotalTileEnergyCut |
Reject events with excess ACD total energy |
89.3% |
1.2% |
AcdTotalTileEventEnergyRatio > .8 or (AcdTkr1ActiveDistENorm > -300 && AcdTotalTileEventEnergyRatio > max(.005, .1 - .0001*AcdTkr1ActiveDistENorm)) |
CornerCut |
Reject event in the corner gap of the ACD |
88.3% |
1.1% |
((Tkr1LATEdge/1.5) ^ 2 + (AcdCornerDocaENorm - 10)^ 2 < 3800 or (Tkr1LATEdge < 80 && abs(AcdCornerDocaENorm-2) < 4)) && Tkr1SSDVeto < 3 |
TileEdgeCut: |
Reject events at tile edges with decreased signal |
88.1% |
1.1% |
abs(AcdTkr1ActiveDistENorm) < 15 && AcdTotalTileEventEnergyRatio > .005 |
ClassificationTree:
Variable |
Importance |
AcdTotalTileEventEnergyRatio |
2034.17 |
Tkr1SSDVeto |
1201.47 |
CTBCORE |
812.28 |
AcdTkr1ActDistNorm |
575.06 |
AcdTkr1ActiveDistENorm |
476.57 |
AcdTotalEnergyNorm |
269.89 |
Tkr1ACDSideZ |
256.61 |
AcdActDistNorm |
118.93 |
Tkr1LATEdge |
107.11 |
AcdTileEnergyNorm |
106.51 |
AcdCornerDocaENorm |
81.52 |
AcdMaxTileEnergy |
74.32 |
AcdTileEventEnergyRatio |
73.48 |
AcdTkr1TileEnergyNorm |
25.67 |
AcdTileCount |
24 |
Using New Variables
AcdTkr1VetoSigmaHit and VetoHit1
AcdTkr1VetoSigmaHit is the probability of the "best" hit vetoing the track, expressed in "sigma". This is the sum in quadrature of contributions from the miss distance and the signal being less that 1 MIP. For MIP signals along the track projection this variable is 0.
Same plot, but with the X-axis remapped with log10( AcdTkr1VetoSigmaHit + 0.01)
For completeness here is a plot of AcdTkr1VetoSigmaHit v. AcdTkr1ActiveDist
VetoHit1 is the same variable, including the tracker SSDVeto.
VetoHit1 = sqrt(Acd2Tkr1VetoSigmaHit*Acd2Tkr1VetoSigmaHit+1.5*Tkr1SSDVeto*Tkr1SSDVeto)
Here is a plot of VetoHit1
Same plot, but the X-axis remapped with log10(VetoHit1+0.01)
Note the small peak in the signal distribution around 7-9 is from low energy deposits in the tile pointed to by the track.
AcdTkr1VetoSigmaGap and VetoGap1
AcdTkr1VetoSigmaGap is the probability that the track went in a gap in the ACD, expressed in "sigma". This is the sum in quadrature of contributions geometrical calculations of the gap and the chance of seeing no signal from the gap. For high energy tracks that pass into the corner gaps of the ACD it is 0. For tracks going into ribbons it is 1.5.
Here is a plot of the low end of AcdTkr1VetoSigmaGap for all events:
For comparison, here is a plot of AcdTkr1VetoSigmaGap v. AcdTkr1RibbonDist:
In analogy with VetoHit1 above we can define VetoGap1 to take into account the Trk1SSDVeto:
VetoGap1 = sqrt(Acd2Tkr1VetoSigmaGap*Acd2Tkr1VetoSigmaGap+1.5*Tkr1SSDVeto*Tkr1SSDVeto)
Here is a plot of the low end of VetoGap1 for all events.
If we look at only those events that pass weren't vetoed because of a track tile association or b/c of excess energy in the ACD we see this:
For Comparison, here is a plot of VetoGap1 v. AcdTkr1RibbonDist for the same set of events.
AcdTkrVetoSigmaHit and VetoHit
We can also select the best association by looping over all tracks.
Here is a plot of that variable, AcdTkrVetoSigmaHit:
In analogy to VetoHit1 we can make VetoHit from AcdTkrVetoSigmaHit.
Here is a plot of that:
Then if we only look at events that weren't rejected because of VetoHit1 or excess energy:
So, we could consider cutting very loose on this and rejecting some event with a high probablity match.
Cut |
Reason |
Gamma Effic |
Bkg Effic |
---|---|---|---|
VetoHit1 < 5 |
Reject events with best rack pointing at struck tile/ribbon |
94.8% |
7.2% |
TotalTileEnergyCut |
Reject events with excess ACD total energy |
89.3% |
1.2% |
VetoGap1 < 2 |
Reject event in gaps of the ACD |
89.1% |
1.2% |
VetoHit < 2 |
Reject events if other track points at hit tile |
89.0% |
1.1% |