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MAPS tracker in DELPHES

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Duccio Abbaneo, Michele Selvaggi (CERN)

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Framework (I)

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  • Implemented as external library (TrackCovariance) by Franco Bedeschi, and called in DELPHES with a dedicated module
  • Tracker Geometry is specified via simple text in Delphes
    • cylinders/disk shapes
      • (zmin, zmax, R) or (Rmin, Rmax, z)
    • active/passive
      • X0 to be specified
      • efficiency per layer (NEW)
    • single/double measurement resolution and corresponding stereo angle
      • 0 : r-phi
      • 𝜋/2 : r-z

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  • e.g IDEA tracker:

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Framework (II)

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  • Original implementation, described in this paper, based on a global 𝜒2 minimisation, involves the inversion of large matrices that contain layer measurement errors (diagonal) and off-diagonal multiple scattering term (e.g. 100x100 for the drift chamber)
    • In order to avoid doing this for every track, at initialisation, the track covariance matrices are calculated at initialisation stage for fixed grid of (p,theta)
    • Track covariance for every track is then derived by means of bi-linear interpolation
    • Track is smeared according to covariance matrix (via Choleski decomposition)
  • Approach well validated, been used for virtually all physics studies that went into FSR

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  • New implementation based on Kalman-Filter
    • iterative, scales better with number of measurements
    • exact (no interpolation)
    • Allows for layer-by-layer inefficiencies (Last entry is a float [0,1] instead of binary)
      • more sophisticated studies can be performed

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Geometry

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IDEA

MAPsTrk

(barrel only)

CLD

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Material Budget

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CLD

MAPsTrk

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Resolution (pT)

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Resolution (d0)

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Resolution (dZ)

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Resolution (theta)

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Resolution (phi)

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Variations

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Resolution - 2T vs 3T

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2T

3T

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Resolution (pixel size)

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5.9 um vs 2.8 um single point resolution in outer tracker

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Vertex detector (v3)

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Additional vertex layer 1.1cm (on the beampipe)

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Conclusion

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  • Delphes can be used to
    • validate tracker resolutions obtained with more sophisticated frameworks (TkLayout, FullSim)
    • run physics analysis on the fly
  • A configuration for CLD, IDEA and MAPsTrk (only barrel) exists

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