Performance of Stripped LAT

1
Performance of Stripped LAT

• Bogdan Pawlik
• INP Krakow
• Bogdan.Pawlik_at_ifj.edu.pl
• Zeuthen
• 26 August 2004

2
LAT description

• LAT consists of 30 tungsten disks, thickness 1X0
  each (0.35 cm)
• Inner /outer radius of disk is respectively 8
  cm/28cm
• Each disk has attached silicon strip detector
  (0.05 cm)
• Every second detector has either 120 radial
  strips to measure azimuthal angle ? or 64
  concentric strips for measurement polar angle ?
• In total there is 15(128120)3720 read-out
  channels
• Advantages 1. low number readout channels
• 2. fine granulation in ?
• 3. entire plane is active ( no dead
  regions)

3
Reconstruction method

• For each LAT disk set of clusters (continuous
  chain of fired strips) is found.
• Their positions is estimated as weighted average
  of fired strip positions
• Weight of a strip is defined as wslog(CEs/Ec)
  where constant C8 was tuned to minimize offset
  and ?(?)
• All clusters from all planes are combined to form
  towers - continuous chain clusters beginning at
  the first plane laying within radius R around
  position of the first cluster

4
Reconstruction method (cont.)

• The longest and best ( min ? ) tower is kept
• The angle is calculated as weighted average
  angles of all clusters forming the tower.
• N.B. This algorithm reduces significantly
  background as isolated clusters and short towers
  are neglected

5
Data Sample

• Events generated with Bhlumi BeamStrahlung at
  250 GeV nominal beam energy
• Events were generated in the range
• 0.7?min ? ? ? 2?max
• Bhabha electrons and photons generated outside
  of the LAT geometrical acceptance can be
  considered as a additional background.

6
Reconstruction results
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Colinearity
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Energy resolution
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Summary

• Stripped LAT with 4000 read-out channels can
  achieve resolution in polar angle ? order of
  4x10-5 radian which results in ?L/L ? 10-3
• Measurement of electron energy can be done with
  accuracy 5GeV (?E0.31vE )
• Need to increase segmentation of ?-planes to
  reach required ?L/L ? 10-4