David Ward

1
Data/MC comparisons

• David Ward
• Have previously reported on comparison of Feb05
  DESY data with Geant4 Monte Carlos.
• Issues with upstream material and tracking
  cutoffs in G4.
• Here give an update using latest modifications in
  Geant4 and Mokka.

2
Recent changes to codes

• Geant4.8.0 changes to e/m processes to reduce
  dependence on tracking cutoffs. Find there is no
  sensitivity to cutoffs in terms of performance
  and little effect on speed.
• Bertini model for Kaons implemented. Need to set
  G4BERTINI_KAON before comiliation of Geant4
  (needed for LCPhys physics list).
• Mokka 5.4 is NOT compatible with GEANT4.8.0.
  Recently received from Paulo a test version
  Mokka_G4.8.0 which is. Mokka 5.5 released last
  night not yet tested.
• Mokka now contains a realistic representation of
  upstream detectors (scintillators, drift
  chambers) thanks to Fabrizio Salvatore (10X0 of
  material)

3
Hit energy /MIPS
All plots 1 GeV electron data / MC
Clearly better, but not perfect
4
Hit energy - tail
5
Total ECAL energy
Still 2-3 discrepancy, but much better
6
No. hits (0.6 MIP threshold)
3 low
7
Energy vs plane
Showering a bit late? Upstream material?
8
Energy in first layer /MIP
10 X0
15 X0
9
Shower barycentre x /mm
Start 1 GeV beam _at_ z-10m as a pencil beam. Beam
width generated by multiple scattering. Almost
correctly.
However, for 2, 3 GeV beam, need 5mm spread _at_
-10m to generate observed width.
10
Shower barycentre y /mm
11
Effect on 10 GeV p- showers?

• Random angles (isotropic)
• Reconstruct clusters using Alex Rasperezas
  TrackwiseClustering (MAGIC gives similar
  trends). Energy scaled by truth.
• Compare LHEP (G4/Mokka default) with LCPhys
  (favoured?) hadronic physics list
• Geant 4.8.0 has the improved electromagnetic
  tracking favoured by CALICE data.
• Typically see effects of 15-25 varying
  versions/options.

Mokka Geant Model Etot Rms E Eecal Ehcal Nclu
4.1 4.7.0? LCPhys 0.959 0.220 0.40 0.56 1.55
5.4 4.7.1_p01 LHEP 0.902 0.196 0.42 0.48 1.39
G4.8.0 4.8.0 LHEP 0.973 0.216 0.45 0.53 1.43
G4.8.0 4.8.0 LCPhys 1.022 0.238 0.42 0.60 1.61