1. Studies of the Time over Threshold
Gamma-ray Large Area Space Telescope
Studies of the Time over Threshold
Monica Brigida
Fabio Gargano
Nicola Giglietto
Francesco Giordano
Francesco Loparco
Nicola Mazziotta
Silvia Rainò
INFN - Bari
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

2. Overview
Study of the redundances in readout electronics (M . Brigida et al.) (2towers data only) no update
Study of the ToT in track layers (F. Loparco et al.) (6towers update):
Analysis of the ToT distributions
Dependence of the ToT on the track parameters (θ,φ)
ToT in X-view and Y-view SSD planes
Study of the ToT overflows
Study of the ToT in triggering layers
Evaluation of the hit capture efficiency
Study of ToT saturating events (N.Giglietto et al.)(2 tw no update)
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

3. Study of the redudancy in the TKR readout: 2 towers analysis
Gamma-ray Large Area Space Telescope
Study of the redudancy in the TKR readout: 2 towers analysis
Monica Brigida
Nico Giglietto
Silvia Rainò
INFN- Bari
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

4. Redudancy in the TKR readout
Outline
Data samples: 2 tower runs
Event Selection
Hit maps per layer
Comparison of
Angular distributions,
Hit multiplicity and ToTs
for runs readout by
LEFT/RIGHT cables only with those read out from both cables
Conclusions
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

5. Event selection and definitions
Trigger from 3 consecutive layers: GemConditionWord = 2
Single tower events: GemTkrVector[tower] ≠ 0 for only one tower
Single muon tracks in the TKR: TkrNumTracks = 1
Track Layers = Layers from Tkr1FirstLayer (First layer in the track) to Tkr1LastLayer (Last layer in the track)
Triggering Layers = The set of 3 layers in a row issuing the trigger request
Actually, we assume that Triggering Layers correspond to the ones from GltLayer to GltLayer+2
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

6. Average ToTs vs layers (3)
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

7. ToT map (Layer 15 Tower 0) ToTs from the right
side of the layer (strip ) seem
to be lower than
the left one
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

8. Conclusions
No anomalies in data readout when comparing left-right and baseline run (but has to check again using calibrated ToTs)
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

9. Study of the Time over Threshold in the 6 towers data samples
Gamma-ray Large Area Space Telescope
Study of the Time over Threshold in the 6 towers data samples
Fabio Gargano
Francesco Loparco
Nicola Mazziotta
INFN - Bari
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

10. Muon cosθ distribution
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

11. Muon φ distribution
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

12. Raw ToT distributions in track layers
Events with ToT=0 have been ruled out The ToT distributions can be fitted by Landau functions: ToT peak value  5.8μs → qmp  4 fC ?
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

13. ToT vs cosθ in track layers
The ToT is minimum for vertical tracks and increases with θ
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

14. 6towers update
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

15. Track length and projected track lengthz z μ μ x y
ToT is proportional to maximum strip pulse amplitude
Pulse amplitudes on strips are proportional to the fraction of track length belonging to their sensitive volume
ToT depends on the track length projected along the strip view
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

16. ToT vs 1/cosθ for track layers
ToT increases linearly with 1/cosθ
ToT increases linearly with track length
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

17. ToT vs 1/cosθ for track layers (updated 6tws)
ToT increases linearly with 1/cosθ
ToT increases linearly with track length
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

18. ToT vs φ for track layers
Average ToT exhibits a periodic dependence on φ (180° period)
X-view layers: maxima at 90° and 270°
Y-view layers: maxima at 0° and 180°
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

19. ToT vs φ for track layers 6tws
Average ToT exhibits a periodic dependence on φ (180° period)
X-view layers: maxima at 90° and 270°
Y-view layers: maxima at 0° and 180°
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

20. ToT, track length and projected track length
Study of the dependence of the ToT on cos
The ToT is a function of the track length
Study of the dependence of the ToT on 
The ToT is a function of the projection of the track length in the SSD plane
We have introduced a new variable: the ratio l/l’
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

21. ToT vs l/l’ in track layers
The ToT depends linearly on l/l’ and increases with the same rate
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

22. ToT vs l/l’ in track layers (6tws)
The ToT depends linearly on l/l’ and increases with the same rate
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

23. ToT vs projected track length: X and Y views
No significant differences in ToT vs l/l’ between X and Y view layers
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

24. ToT vs projected track length: X and Y views (6tw)
No significant differences in ToT vs l/l’ between X and Y view layers
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

25. Study of ToT overflows in track layers
We have studied the ToT overflows as a function of:
tower planes to look for eventual noisy planes
track parameters (θ, φ) to search for eventual anomalies
Experimental data show that:
The fraction of overflows fluctuates among the planes
As expected, the fraction of overflows increases with increasing track length
The fraction of overflow shows a small dependence on the φ angle for the Tower 0 data sample small difference between the average response of X-view and Y-view layers
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

26. ToT overflows in SSD layers
The average behavior of the 4 towers is the same. The number of overflows fluctuates among the planes
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

27. ToT overflows in SSD layers (6tw)
The average behavior of the 4 towers is the same. The number of overflows fluctuates among the planes
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

28. ToT overflows vs cosθ All towers exhibit the same behavior
The fraction of ToT overflows increases with increasing track length
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

29. ToT overflows vs cosθ (6tws)
All towers exhibit the same behavior
The fraction of ToT overflows increases with increasing track length
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

30. ToT overflows vs φ
Fraction of overflows in Tower 0 seems to depend on φ with a period of 90° . This effect could be caused by small differences between the average behavior of SSDs in X-view and Y-view layers
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

31. ToT overflows vs φ (6tws)
Fraction of overflows in Tower 0 seems to depend on φ with a period of 90° . This effect could be caused by small differences between the average behavior of SSDs in X-view and Y-view layers
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

32. ToT in triggering layers
Why studying ToT in triggering layers?
To generate a trigger, a coincidence among 3 layers (6 planes) in a row is requested the probability of a noisy plane being involved in the trigger is negligible
The study of hit distributions in triggering layers allows to get an estimate of the SSD hit capture efficiency
Which are the triggering layers?
Actually, we assume that triggering layers are the ones from GltLayer to GltLayer+2
we know that GltLayer corresponds to the first layer of the lowest “3 in a row” possible combination
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

33. ToT distributions in triggering layers
In this case events with ToT = 0 have been included!
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

34. Estimate of hit capture efficiency
Tower 0: 1-ε = 3.0×10-3
Tower 1: 1-ε = 0.7×10-3
Tower 2: 1-ε = 0.6×10-3
Tower 3: 1-ε = 0.5×10-3
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

35. Conclusions The ToT distributions can be fitted with Landau functions
The dependence of ToT on the track parameters θ and φ has been investigated
The ToT increases linearly with 1/cosθ (as expected)
The ToT increases linearly with l/l’
An analysis of the ToT overflows has been performed
The ToT in triggering layers has been studied
Hit capture efficiencies of all LAT Towers are > 99%
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

36. Requests & future plans
ToT conversion in charge units (fC)
to provide an absolute measurement of energy deposited in SSDs for all strips
as a feedback for the simulations
Information, in the digi files, about the hit positions (a pair of xz or yz coordinates related to each hit)
to study single strip efficiencies
to perform further studies:
analysis of spurious hits
search for stopping muons …
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

37. ToT saturated events: a preliminary study
N.Giglietto-M. Brigida
F.Giordano
Science
Verification,
Analysis and
Calibrations
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

38. A study on the events saturating ToTs
Question: ToT values in saturation are really high energy deposit?
Answer: probably yes, but has to be checked
Strategy to understand this simple situation:
1) define a clean class of event (i.e low energy muons and high energy events)
2) look to the ToT distribution and compare with the whole distribution
3) event display to verify
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

39. Muon and shower definition
We define as muon the event with the following characteristics:
Single track
1 Mip deposit in calorimeter (0.6<CALMIP<1.3)
Moreover we use almost vertical event (Zdir <-0.95) We define as shower a showering event characterized by:
>1 Mip deposit in calorimeter or
Many hits (total or outside the track) in tracker
Many tracks
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

40. What are the keys to select shower?
Showers should be characterized by many hits or many tracks or bad chi^2 in the reconstruction
Here shower is defined
as TRACK>1 or event with
CALMIP>1.3
Showers are characterized by
Many hits out of track (>40-60)
or bad chi^2 in the first track
or many total hits (>70?)
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

41. ToTs All ToTs in all active layers Fraction of ToT saturations:
0.21 % all events
0.05 % muons
0.31 % showers
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

42. ToT saturations indicate really
Conclusions
Muons have fewer fractions of ToT saturations
Showers (defined looking only hits or CAL) have a larger fraction of ToT saturations
ToT saturations indicate really
large energy deposits
Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005