Workshop on Forward Calorimetry Prague, April 16 Impact of Bhabha scattering on the BeamCal performances

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Workshop on Forward CalorimetryPrague, April
16Impact of Bhabha scattering on the BeamCal
performances
Vladimir Drugakov NC PHEP, Minsk/DESY
Zeuthen Andrey Elagin JINR, Dubna
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Motivation

• Benchmark geometry of the BeamCal
• 5 mrad ? 28 mrad, where 5 mrad ?BeamPipe
  5.45 mrad
• Bhabha scattering e- e -gt e- e (n?)
• s 1/?3 gt very high probability at very small
  angles
• When one or several particle from such event
  are found but event is not identified like
  Bhabha, it becomes severe backgroud for other
  physic processes.
• Why some events cannot be fully reconstructed
  and identified
• - some particles are lost
• - pure energy resolution
• Why particles can be lost
• - reconstruction problem due to beamstrahlung
  background
• - kinematics - ?-radiation deflect particles.

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Beamstrahlung Background
R-f distribution of energy flux for particular BX
.
Energy flux through particular cell. Train
dynamics.
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Single Electron Reconstruction Efficiency
a) and b) represents different f angles
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Bhabha kinematics
Examples
BHLUMI generator Tmin 0.3 mrad
?
e-
e
Total Probability 0.85 BX-1
e-
e
?
Only 1 electron hits detector
How correct it works at such small angles?
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TEEGG generator
Generate process e- e -gt e- e
?(?) Options - only 1 e- or e in detector -
only ? in detector
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Reconstruction
First step is to simulate and reconstruct e- e
-gt e- e process
BHLUMI generator Total Probability 0.11
BX-1 Hit BP 11.5 1000 event were tracked by
BRAHMS and then reconstructed - 10.5 - 0 e -
leakage - 6.7 - 1 e - leakage
reconstruction imperfection - 82.2 - 2 e
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Reconstruction. Angular resolution.
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Reconstruction. Energy resolution and cuts
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Outlook

• A lot of work is to be done
• Verify BHLUMI reliability at submrad angles
• (Analysing full Bhabha event zoo)
• Find out identification criteria
• Find out minimal angle
• Finally Find out reconstruction rate
• Find out veto rate