Time over Threshold studies: a brief history

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Time over Threshold studies a brief history

• Bari group

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LAT Tracker digital signal read-out

• The electronics chain consists of charge
  preamplifier, shaper and comparator
• The front-end electronics has been designed to
  evaluate the charge collected by the strips from
  the Time-over-Threshold (ToT).
• LAT-TD-1058 (10-21-02)

• Digital Output
• IDs of fired strips
• ToT per layer
• (i.e. ORing per layer)

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Digitization ToT generation

• m.i.p.in 400µm of Si
• ltElossgt 150 keV
• Npairs 104 e-h
• Qdep 5-6 fC

ToT (mip) 8 µs
The ToT is an extimator of collected charge
ToT 1.6 µs/fC
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ToT for ? and charged particles
If electron and positron from ? conversion
release charge on a single strip, a double ToT
value is expected
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ToT distribution for ?-rays
ToT (200ns step)
. depends on the ?-rays energy
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Average ToT for charged particles
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TKR L1 trigger simulationLAT-TD-04184 (June 18,
2004)
L1 trigger

• 6-fold coincidence
• (first 3-x and 3-y hit layers)
• Tc is the time coincidence

The strip is captured if T2-Tc gt ?Td (2µs)
where ?Td is the trigger acknowledgement
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Hit capture efficiency (Vth 160mV)
100 captured hit
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ToT studies for the Instrument Analysis
The ToT increases linearly with 1/cos? (track
length)
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ToT map (Layer 15 Tower 0)
ToTs from the right side of the layer (strip
768-1535) seem to be lower than the left one .
To be continued
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Conclusions what the ToT can tell us ?

• PID
• Heavy nuclei primaries identif. (in flight) (5mip
  dinamical range-gt p/He)
• Energy deposition in Si layers
• Further analysis are planned
• Efficiency studies
• Calibration tests (µ stops in the Tracker)
• Vertex reconstruction
• Study of ToT related variables in ntuples (are
  now well choosen?)