1. Full Sim Status
Estel Perez
27 July 2017

2. Introduction Focusing on tracking efficiency at pT(b)=5000 GeV.
theta distribution (reconstructable)
Focusing on tracking efficiency at pT(b)=5000 GeV.
Why is it so low in the central region?
Checked dependence on:
heavy flavour vs light flavour jet events
Magnetic field
Vertex and tracker granularity
eff vs theta (reconstructed/reconstructable)
why this drop?

3. Compare heavy flavor (bb) vs light flavor (ll) jet events
theta distribution (reconstructable)
bb sample
ll sample
eff vs theta (reconstructed/reconstructable)
 Effect less visible in the light flavor jet sample

4. is it because B-jets have displaced tracks?
BC-had daughters
non BC-had daughters
Not completely: even if they are not displaced, BC-hadron daughters
have lower efficiency
maybe because B/C-hadron daughters are closer to each other?

5. tracks are too close to each other?
 plot distance to the closest mcp (charged, stable, pt>1GeV)
(there can still be hits from other non-stable or lower pT particles)
ll sample
When we consider non-displaced tracks, the efficiency curve vs distance to the closest track is very similar (1,2,4). However, B&C-hadron daughters have more often a very close-by track, and therefore they have lower global efficiency
bb sample
B&C-hadron daughters only
without B&C-hadron daughters
rvtx<20mm
Tracking efficiency vs distance to closest mc particle
Distance to closest mc particle 1 2 3 4

6. Overall Efficiency
default Granularity
ll Eff =
rvtx<20mm Eff =
bb Eff =
B/C hadron, rvtx>20mm Eff =
B/C hadron, rvtx<20mm Eff =
! B/C hadron, rvtx<20mm Eff =
compare heavy flavour and light flavour jets: see the effect of the displaced tracks
(LF jets have more tracks, of lower pT)
(remove displaced tracks caused by interaction with the material)
HF jets have some displaced tracks
-> B/C hadron daughters (very displaced > 20mm)
-> B/C hadron daughters (little displaced < 20mm)
-> all but B/C hadron daughters (little displaced < 20mm)
Effect of B/C-hadron decays giving tracks that are more collimated than LF-hadron decays
Effect of B/C-hadron decays giving highly displaced tracks

7. default Granularity B=6T
Could we recover some of the efficiency by separating the track hits further ?
If we would increase the magnetic field, tracks of different charges or asymmetric pT would be easier to separate
default Granularity
default Granularity B=6T
ll Eff =
PurityEff =
bb Eff =
Efficiency gets slightly worse (because tracks with pt<1.5 GeV are lost – was 1GeV with 4T)
but purity increases significantly (12-15%)  To be investigated, probably many fake low pT tracks are lost as well.

8. Half Pitch in RPhi barrel
Could we recover some of the efficiency by being able to reconstruct close-by hits ?
If we would increase the granularity (of the tracker and vertex detector), close-by hits would be easier to reconstruct as such and we’d be able to resolve close-by tracks
default Granularity
Half Pitch in RPhi barrel
Half Pitch in Rphi and z
ll Eff =
PurityEff =
bb Eff =
B/C hadron Eff =
Resolution in z does have an impact on tracking efficiency (specially in the purity, to be investigated). In the 8th to last layer the pitch is 0.033x0.100 mm, only a factor of 3, so when I set half the z pitch , the Rphi and z pitches become comparable and therefore both relevant.

9. default Granularity B=6T Half Pitch in RPhi barrel
Summary
default Granularity
default Granularity B=6T
Half Pitch in RPhi barrel
Half Pitch in Rphi and z
ll Eff =
PurityEff =
bb Eff =
B/C hadron Eff =
Improving the granularity moderately improves the tracking efficiency
It significantly improves the purity – comparable to increasing the B field to 6T

10. Next steps Implement V3.03 (4 close-by layers)
Compare flavor tagging performance
Document

11. Backup

12. Recap from past meetings
Tracking Efficiency degrades with jet pT
Not due to d0 cut
Due (at least partially) to hit confusion: tracks are closer and also they have higher pT so they bend less
50 GeV
500 GeV
5000 GeV
8 hits
7 hits
6 hits

13. Opt3_v02a single point resolution pitch [mm] 10x15000 µm 0.033x51.2

14. Efficiency vs single point resolution
min 8 hits  look at separation at 8th to last layer
Efficiency vs single point resolution
Central B-jets
pT(Bjet)=10 TeV
pT(Bjet)=5 TeV
pT(Bjet)=2 TeV
pT(Bjet)=1 TeV
pT(Bjet)=500 GeV
pT(Bjet)=200 GeV
pT(Bjet)=100 GeV
pT(Bjet)=50 GeV
high pt samples: it does not get worse anymore since some of the particles have not decayed yet (only considering status 1 particles

15. Efficiency definition (II)
C-hadron
Consider only the hits produced by the daughters of the long-lived B and C-hadrons
Require generator status==1
Assume: we need to separate the closest pair of daughters
 Consider the closest pair of hits in the 4th-to-last layer
B-hadron

16. ll 5000 default Granularity

17. ll 5000 default Granularity 6T

18. ll 5000 half Pitch

19. bb 5000 default Granularity

20. bb 5000 default Granularity 6T

21. bb 5000 half pitch

22. bb 5000 default Granularity (only particles from B/C hadron decay)

23. bb 5000 half pitch (only particles from B/C hadron decay)

24. Possibilities: Tracks too close to each other
hit confusion -> low track purity -> low mcp<->track matching efficiency
tried loosening track matching purity
(bb evts, B&C hadron daughters only)
>75%: global Eff = 0.445
>50%: global Eff = 0.526
 this is partially the cause

25. Efficiency vs single point resolution
look at separation at 4th to last layer
Efficiency vs single point resolution
Vertical line shows the default 10x100 [μm]
pT(Bjet)=10 TeV
pT(Bjet)=5 TeV
pT(Bjet)=2 TeV
pT(Bjet)=1 TeV
pT(Bjet)=500 GeV
pT(Bjet)=200 GeV
pT(Bjet)=100 GeV
pT(Bjet)=50 GeV

26. Efficiency vs single point resolution
look at separation at 6th to last layer
Efficiency vs single point resolution
Central B-jets
pT(Bjet)=10 TeV
pT(Bjet)=5 TeV
pT(Bjet)=2 TeV
pT(Bjet)=1 TeV
pT(Bjet)=500 GeV
pT(Bjet)=200 GeV
pT(Bjet)=100 GeV
pT(Bjet)=50 GeV

27. Tracking at high jet pT
MC particle Efficiency: reconstructed/reconstructable
Reconstructable: mc particle (pt>0.1GeV, cosTheta<0.99)
charged
stable (generatorStatus==1)
At least 4 hits associated
Reconstructed
There’s a track with >75% of its hits associated to this mcp
Track Purity: pure/reconstructed
Reconstructed: track
Pure: track with 75% of its hits coming from the same mcp

28. overall Eff vs Purity as function on min Num of Hits in track
50 GeV
500 GeV
5000 GeV
8 hits
7 hits
6 hits

29. overall Eff vs Purity as function of min Num of Hits in track for tracks coming from B or C hadrons & their daughters
8 hits
7 hits
6 hits
8 hits
50 GeV
500 GeV
5000 GeV
7 hits
8 hits
6 hits
7 hits
6 hits

30. Why such low efficiency?
Check efficiency dependence on jet PT

31. 500 GeV 8 hits Top: reconstructable mc particles; Bottom: efficiencyPt
R prod vtx d0 z0
theta
DRclosest mcp

32. 1000 GeV 8 hits Top: reconstructable mc particles; Bottom: efficiencyPt
R prod vtx d0 z0
theta
DRclosest mcp
efficiency for close-by particles starts dropping

33. 2000 GeV 8 hits Top: reconstructable mc particles; Bottom: efficiencyPt
R prod vtx d0 z0
theta
DRclosest mcp
efficiency for very central particles starts dropping

34. dramatic drop in theta and DR
5000 GeV 8 hits
Top: reconstructable mc particles; Bottom: efficiency Pt
R prod vtx d0 z0
theta
DRclosest mcp
dramatic drop in theta and DR
not only tracks are closer, but they have higher pT so they bend less

35. Tried open up d0 cut  eff did not change narrow down badchi2 cut
d0<10 mm: global Eff = 0.445
d0<20 mm: global Eff = 0.446
d0<20 mm: global Eff = 0.445
narrow down badchi2 cut
badchi2 <5: global Eff = – default
badchi2 <3: global Eff = 0.458
loose track matching purity
>75%: global Eff = 0.445
>50%: global Eff = 0.526

36. purity for mcp<->track matching = 75%
Eff = 0.445

37. purity for mcp<->track matching = 50%
Eff = 0.526
When we relax the matching criteria, the efficiency improves  inefficiency due (at least partially) to hit confusion

39. min 8 hits  look at separayion at 8th to last layer
Central B-jets
pT(Bjet)=10 TeV
pT(Bjet)=5 TeV
pT(Bjet)=2 TeV
pT(Bjet)=1 TeV
pT(Bjet)=500 GeV
pT(Bjet)=200 GeV
pT(Bjet)=100 GeV
pT(Bjet)=50 GeV

40. look at separation at 6th to last layer
Central B-jets
pT(Bjet)=10 TeV
pT(Bjet)=5 TeV
pT(Bjet)=2 TeV
pT(Bjet)=1 TeV
pT(Bjet)=500 GeV
pT(Bjet)=200 GeV
pT(Bjet)=100 GeV
pT(Bjet)=50 GeV

41. look at separation at 4th to last layer
Central B-jets
pT(Bjet)=10 TeV
pT(Bjet)=5 TeV
pT(Bjet)=2 TeV
pT(Bjet)=1 TeV
pT(Bjet)=500 GeV
pT(Bjet)=200 GeV
pT(Bjet)=100 GeV
pT(Bjet)=50 GeV

42. layer1
layer2
layer3
layer4
layer5
layer6
layer7
layer1
layer2
layer3
layer4
layer5
layer6
pass