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Design Parameters of LumiCal

FCAL. Collaboration High precision design. Design Parameters of LumiCal. Iftach Sadeh Tel Aviv University DESY. Feb 5 th 2008. The factors to be considered. Stable Energy Resolution : - Impose Cuts on the fiducial volume (define: [θ min , θ max ]).

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Design Parameters of LumiCal

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  1. FCAL CollaborationHigh precision design Design Parametersof LumiCal Iftach SadehTel Aviv UniversityDESY Feb 5th 2008

  2. The factors to be considered Stable Energy Resolution:- Impose Cuts on the fiducial volume (define: [θmin, θmax]). Range of induced charge (from MIPs to 250 GeV electron showers):- Depends on the size of the cells. Decide on inner and outer radii:- Determines the magnitude of the integrated Bhabha cross section.- Determines the amount of backscattering in other parts of the detector (not shown here). Number of radial divisions (cylinders):- Determines the angular resolution (σ(θ) ) and bias (Δθ). Thickness of the tungsten:- Determines the energy resolution.- Prevention of back leakage requires modifying the number of layers.

  3. Induced charge (MIP / electron shower) Electron Signal MIP Signal MAX signal in an event

  4. Number of cylinders sector cylinder Y X

  5. Luminosity error for different radii • For Rmin ≥ 70 mm , the amount of backscattering in other parts of the detector is manageable.(Shown at the Oct’ 2007 FCAL meeting)

  6. 3.0 mm Tungsten → ~ Order of magnitude less θ bias

  7. Energy resolution : 3.5 mm Tungsten • The energy resolution for a LumiCal with 30 and with 90 layers is the same → there is no significant energy deposition at layers > 30 → there is no back-leakage.

  8. 3.0 mm Tungsten → Need 45 layers to match the total thickness to (the original) 30 X0

  9. Are there high-charge tails ? • Bogdan got high energy tails to the distribution of the maximal event cell charge. • This doesn’t seems to be the case here.

  10. Muon hit-energy distribution • There was a strange bump (right arrow) and some very low energy hits (left arrow) in the distribution.

  11. Muon hit-energy distribution : Corrections A muon is close to, but not fully equivalent to a MIP Despite this being a muon distribution, there are still new particles generated in the tungsten and these create (low energy) showers → Ignore these contributions , and simulate LumiCal with one layer only. Other processes besides ionization take place (bremsstrahlung, pair production) → Turn off all muon processes but ionization in the geant4 MC. There are border effects between cells →simulate LumiCal with one cell (no radial and no azimuthal divisions).

  12. Muon hit-energy distribution : Corrections • Now everything is fine…

  13. Moliere radius for two tungsten thicknesses • The Moliere radius increases for thinner tungsten, but the difference in insignificant…

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