Scanning 6 GeV electrons

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Electron analysis

• Scanning 6 GeV electrons
• Electron identication
• Energy measurement

F. Juget Neuchâtel 9th december
2
Scanning

• Brick with 6 GeV electrons (100/cm2)
• With only 20 sheets
• 12 electrons spots of 400 electrons each

• Scanned (dry) the 20 sheets
• 10 cm2 ( 2 electrons spots)
• Recontructed with FEDRA

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Scanning results
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(No Transcript)
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Electron identification

• Take only reconstructed tracks starting in the
  first emulsion
• with no hole
• at least 3 segments
• Electron identification 2 independant method
• Use the energy lost (gtmore scattering compare
  to p)
• c2 method
• Counting tracks started in a cylinder centered
  on the electron candidate along the whole length
  of the brick

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Energy lost and scattering
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c2 difference vs number of segments
Dc2 lt 0 e-like
Dc2 gt 0 p-like
In beam slope
Out beam slope
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Number of tracks

• Counting tracks
• With at least 3 segments
• starting in a cylinder of 100 mm radius along the
  track candidate for the total lenght of the brick
• The size of the radius can be optimized with
  pions (50 mm, 25 mm)?

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Number of tracks
Cuts Efficiency
electron
pion R 100mm N 4
90 2 R 100mm N 3
90-100 5 R 100mm N 2
100 15 R 50mm N 2
100 10 R 50mm N 3
70 2

• Pion
• july test beam
• 10 lead layers
• 4 GeV

• ID improvement with
• c2
• Infos on the shower

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Number of tracks
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Energy measurement

• With the selected tracks (cylinder 100 mm with
  nbr tracks 3)
• Counting, for each emulsion, the number of
  basetracks in a cylinder centered on the electron
  track along the whole brick (20 sheets)
• Different radius 200 mm, 500 mm 1000 mm
  (problem of shower overlapp?)

Each emulsion have different basetrack density
(scanning parameters dependent) gt need a
background subtraction procedure for each
emulsion
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Background estimation

• Between the 2 electrons spots (no tracks, almost
  only background)
• Counting the number of basetracks for each
  emulsion in the cylinder
• Fluctuation? Homogeneus? Scanning parameters? .

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 Electron  tracks
Background estimation
After background subtraction
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 No electron 
Background estimation
After background subtraction
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Linear fit of the first 11 sheets (10 lead
layers 1.8 X0)
Simulated dE/dx (from pdg)
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Conclusion

• Scan (dry) and reconstruct successfully electron
  tracks with the shower
• Electron ID can be optimised combining
• c2 (energy lost)
• Number of tracks starting in a small cylinder
• Optimisation of the radius?
• Informations on the shower
• Energy measurement
• Possible to count basetracks in a cylinder and
  extract a distribution of dE/dx
• optimisation of the radius
• Background subtraction procedure has to be done
  properly
• The fluctuation should be large? (factor 2 or 3)
• We need for a correct estimation
• Other energies 3 GeV (Lyon) 1 GeV (Italy)
• Less density (50/cm2 1 GeV) (1/cm2 3 GeV
  and 6 GeV)
• Larger statitics (in our brick we have 4000
  electrons, but high density)