1. Time Independent Analysis
Asl at LHCb
Time Independent Analysis

2. Re-cap
To look at the L0Muon trigger we have used the tag and probe sample requiring that:
The probe is TIS as all trigger levels
The probe passes the Asl muon cuts
From this sample we then look at the efficiency of the L0 trigger, i.e. what fraction of sample has probe TOS on L0 muon trigger.
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

3. Re-cap Asymmetry observed using J/Psi’s in L0:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

4. The Plan I decided to investigate this further to see.
Where is this ~ 5% coming from?
Could it be related to tag and probe correlations?
Look in bins of momentum (same as Asl analysis) an then look at specific projections on the X-Y plane of muon station 3.
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

5. X vs Y vs P
I find it is useful to look at the ‘reflected region’ on the detector for the following plots. I.e. Mu+ efficiency as a fraction of the Mu- efficiency on the other side of the detector (about Y-axis):
e.g. Mu(+) in this bin…
… with Mu(-) in this bin
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

6. Left side approximately consistent with 1
X vs Y vs P - 1
In all previous muon efficiency studies I have found that efficiencies in reflected bins give answers consistent with 1.
Here we see up to ~10% asymmetry on right side of detector for Magnet Down.
Approximately the opposite effect is seen for the left side of Magnet Up.
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Left side approximately consistent with 1
Right side is not…

7. X vs Y vs P - 2
And for the other bins of momentum the same left right differences are seen:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
(though the relative proportion of events in particular geometric areas changes with momentum. i.e higher momentum muons are grouped more around the peampipe. See backup for yields in each bin)

8. X vs Y vs P - 3
And for the other bins of momentum the same left right differences are seen:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

9. X vs Y vs P - 4
And for the other bins of momentum the same left right differences are seen:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

10. X vs Y vs P - 5
And for the other bins of momentum the same left right differences are seen:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

11. X vs Y vs P - 6
And for the other bins of momentum the same left right differences are seen:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

12. Inefficiency Source What do these plots show? Magnet Down: Magnet Up:
Efficiency of inward bending muons is the same (red lines).
Efficiency of outward bending tracks is different, right side is less efficient than left.
i.e. μ+DL ≈ μ-DR; μ-DL > μ+DR; μ-UL ≈ μ+UR; μ+UL > μ-UR,
μ-DR
μ+DR
μ+DL
μ-DL
μ+UR
μ-UR
μ-UL
μ+UL
Magnet Down:
Magnet Up:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

13. Inefficiency Source - 1
Conclusion: Both magnet polarities are consistent with a decrease in efficiency on the right-hand side of the detector relative to the left-hand side – but only for tracks bending away from the beampipe.
To investigate further I look at a particular bin in which we see the effect:
Bin definition:
Magnet Down
P: 6->20 GeV/c
Y: > mm
Mu(+) - X: 500->1500 mm
Mu(-) - X: > -500 mm
This bin has a 10% asymmetry and is not next to the beampipe or at the outer X acceptance of the chamber.
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

14. Inefficiency Source - 2 Magnet Down Yield of all candidates: Mu(-):
(normalised to 1)
Mu(-):
Mu(+):
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Muon distributions are symmetric.

15. Inefficiency Source - 3 Magnet Down L0 Muon efficiency bin by bin:
(for each bin on plots from previous slide simply divide number that are L0Muon TOS by total bin population)
Mu(-):
Mu(+):
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Region with Y > is mostly green/yellow for mu(-) and mostly blue/green for mu(+) – this is where the majority of the data is located.
(also there an essentially ‘dead’ region for the mu+, but I don’t think this is the dominant contributor to efficiency loss.)

16. Inefficiency Source - 4 Magnet Down
Check: Both muon charges in these bins have comparable momentum distributions
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

17. Inefficiency Source - 5 Lets look at another bin:
Highest stats are in these bins. E.g. for mu(-)
Bin definition:
Magnet Down
P: 40->50 GeV/c
Y: > 500 mm
Mu(+) - X: 500->1500 mm
Mu(-) - X: > -500 mm
This bin has a ~20% asymmetry and has a large fraction of the statistics for this momentum range.
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

18. Inefficiency Source - 6 Magnet Down Yield of all candidates: Mu(-):
(normalised to 1)
Mu(-):
Mu(+):
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Muon distributions are symmetric.

19. Inefficiency Source - 7 Magnet Down L0 Muon efficiency bin by bin:
(simply divide number that are L0Muon TOS by total bin population)
Mu(-):
Mu(+):
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Again the region with the most statistics (-1000<X<-600 for mu(-) and 600>X>1000 for mu(+)) shows large difference in L0Muon efficiency.

20. Inefficiency Source - 8 Magnet Down
Check: Both muon charges in these bins have comparable momentum distributions
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Here mu(+) has slightly lower fraction of low Pt tracks – however, this should make the mu(+) relatively more efficient i.e. it will slightly reduce the asymmetry we observe.

21. Alternative data subsets
With the J/Psi tag and probe calibration sample the asymmetry is clearly there. Could this be due to correlations between the tag and probe?
Instead of simply requiring the probe to be TIS I also looked at:
When the JPsi is TIS - i.e. something other than the two muons associated with the Jpsi triggered the event.
When both the tag and probe are TIS
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

22. Alternative data subsets
The asymmetry is there to a large degree in momentum for both these data subsets:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

23. Alternative data subsets
And also in Pt:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc
Bias vs Pt is consistent between just ‘probe TIS’ and ‘Jpsi TIS’.
It is smaller when we require the tag and probe to be TIS: Could be the effect Mika showed, i.e. forcing a higher efficiency reduces magnitude of asymmetry.

24. Alternative data subsets
The Pt distributions of there three samples (and the Asl selected data):
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

25. X vs Y vs Pt
Instead of P vx X vs Y it is possibly more interesting to look at Pt vs X vs Y for L0 efficiencies. A couple of examples:
Low Pt:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

26. X vs Y vs Pt
Instead of P vx X vs Y it is possibly more interesting to look at Pt vs X vs Y for L0 efficiencies. A couple of examples:
High Pt:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

27. Summary
It appears there is a detector asymmetry (chamber mis-alignment on right hand side?), which is most significant for low Pt tracks:
Effect is reduced when distributions are selected such that they have smaller Pt contribution.
Solution: Re-weight sample to match signal Pt distribution?
It will be very interesting to see if Zhou comes to similar conclusions!
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

28. X vs Y vs P Magnet Down 6-20 GeV/c- Efficiency
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

29. X vs Y vs P Magnet Down 6-20 GeV/c- Efficiency ratio +/- Yields:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

30. X vs Y vs P Magnet Down 20-30 GeV/c- Efficiency
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

31. X vs Y vs P Magnet Down 20-30 GeV/c- Efficiency ratio +/- Yields:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

32. X vs Y vs P Magnet Down 30-40 GeV/c- Efficiency
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

33. X vs Y vs P Magnet Down 30-40 GeV/c- Efficiency ratio +/- Yields:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

34. X vs Y vs P Magnet Down 40-50 GeV/c- Efficiency
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

35. X vs Y vs P Magnet Down 40-50 GeV/c- Efficiency ratio +/- Yields:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

36. X vs Y vs P Magnet Down 50-70 GeV/c- Efficiency
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

37. X vs Y vs P Magnet Down 50-70 GeV/c- Efficiency ratio +/- Yields:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

38. X vs Y vs P Magnet Down 70-100 GeV/c- Efficiency
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc

39. X vs Y vs P Magnet Down 70-100 GeV/c- Efficiency ratio +/- Yields:
Nee dot measure delta ms so we know the fine proper time resolution/ lifetime ratios so we undertand the proper time etc