InDet Tracking Performance Plots from the CSC Book

Explanation for Figures

• A full version of the InDet Tracking Performance CSC chapter is available via CDS (ATL-COM-PHYS-2008-105)
• If you want to cite the CSC book in your publication, please do it the following way:
  ATLAS Collaboration,
  Expected Performance of the ATLAS Experiment,
Detector, Trigger and Physics,
CERN-OPEN-2008-020, Geneva, 2008, to appear.
• An .eps version of each of the plots displayed below is available by clicking on the corresponding thumbnail.
  Thanks to Wolfgang Mader for help with this layout.

Plots

Introduction

	Figure 1: Cut-away view of the ATLAS inner detector.
	Figure 2: Plan view of a quarter-section of the ATLAS inner detector showing each of the major elements with its active dimensions.
	Figure 3: Material distribution (X0, λ) at the exit of the ID envelope, including the services and thermal enclosures. The distribution is shown as a function of |η| and averaged over φ. The breakdown indicates the contributions of external services and of individual sub-detectors, including services in their active volume.

Tracking Performance

Track Parameter Resolutions

	Figure 3: Relative transverse momentum resolution (upper) as a function of |η| for muons with pT=1, 5 and 100GeV. Transverse momentum (lower), at which the multiple-scattering contribution equals the intrinsic resolution, as a function of |η|.
	Figure 5: Transverse impact parameter resolution (upper) as a function of |η| for muons with pT=1, 5 and 100GeV. Transverse momentum (lower), at which the multiple-scattering contribution equals the intrinsic resolution, as a function of |η|.
	Figure 6: Modified longitudinal impact parameter resolution (upper) as a function of |η| for muons with pT=1, 5 and 100GeV. Transverse momentum (lower), at which the multiple-scattering contribution equals the intrinsic resolution, as a function of |η|.
	Figure 7: Resolution of the transverse impact parameter, d0 (left) and the modified longitudinal impact parameter, z0 x sinθ (right) for 5GeV muons and pions with |η|<0.5 - corresponding to the first two bins of the previous two figures.
	Figure 8: Probability for the reconstructed invariant mass of muon pairs from J/ψ→μμ decays in events with prompt J/ψ production. Distributions are shown for both muons with |η|<0.8 (left) and |η| >1.5 (right).
	Figure 9: Reconstructed inverse transverse momentum multiplied by the charge for high-energy muons (μ-) (left) and electrons (e-) (right) for pT=0.5TeV (top) and pT=2TeV (bottom) and integrated over a flat distribution in η with |η|<2.5. Those tracks which have been incorrectly reconstructed with a positive charge are indicated by the shaded regions. At 2TeV, the fraction of electrons (muons) whose charge has been misidentified is 12.8% (13.7%).
	Figure 10: Charge misidentification probability for high-energy muons and electrons as a function of pT for particles with |η|<2.5 (upper) and as a function of |η| for pT=2TeV (lower).

Track reconstruction Efficiency

	Figure 11: Track reconstruction efficiencies as a function of |η| for muons (upper) and pions (lower) with pT=1,5 and 100GeV.
	Figure 12: Track reconstruction efficiencies as a function of |η| for electrons with pT=1,5 and 100GeV.
	Figure 13: Track reconstruction efficiencies as a function of |η| for muons, pions and electrons with pT=5GeV. The inefficiencies for pions and electrons reflect the shape of the amount of material in the inner detector as a function of |η|.
	Figure 14: Track reconstruction efficiencies and fake rates as a function of |η| for charged pions in jets in ttbar events and for different quality cuts. "Reconstruction" refers to the basic reconstruction before additional quality cuts.
	Figure 15: Track reconstruction efficiencies and fake rates as a function of the distance ΔR (defined as ΔR = sqrt{Δη2+Δφ2}) of the track to the jet axis, using the standard quality cuts and integrated over |η|<2.5, for charged pions in jets in ttbar events.

Figure 16: Track reconstruction efficiencies as a function of pT for |η|<2.5 and pT>0.1GeV (upper) and as a function of |η| for two different pT ranges (lower) in minimum bias events (non-diffractive inelastic events).

	Figure 17: Rate of candidate fake tracks as a function of pT for |η|< 2.5 and pT> 0.1GeV (upper) and as a function of |η| (lower) in minimum bias events (non-diffractive inelastic events). The rate of such tracks is a function of the amount of material, indicating that a large fraction of them are secondaries for which the Monte-Carlo truth information is not kept

Vertexing Performance

Primary Vertices

	Figure 18: Primary vertex residual along x, in the transverse plane (upper), and along z, parallel to the beam (lower), for events containing top-quark pairs and Hγγ decays with mHM=120GeV. The results are shown without pile-up and without any beam constraint.

Secondary Vertices

	Figure 19: Resolution for the reconstruction of the radial position of the secondary vertex for J/ψ→μμ decays in events containing B-hadron decays for tracks with |η| around 0 (upper) and as a function of the pseudorapidity of the J/ψ (lower). The J/ψ have an average transverse momentum of 15GeV.
	Figure 20: Resolution for the reconstruction of the radial position of the secondary vertex for three-prong hadronic τ-decays in Z→ττ events for tracks with |η| around 0 (upper) and as a function of the pseudorapidity of the τ (lower). In the lower plot, the circles with bars correspond to Gaussian fits, as illustrated in the upper plot; the points showing 68.3% (95%) coverage show the width of the integrated distribution containing 68.3% (95%) of the measurements (corresponding to 1σ (2σ) for a Gaussian distribution). The τ-leptons have an average transverse momentum of 36GeV.
	Figure 21: Resolution for the reconstructed radial position of the secondary vertex for K0s→π+π- decays in events containing B-hadron decays in various radial intervals (upper) and as a function of the K0s decay radius (lower). The resolutions are best for decays just in front of the detector layers. The barrel pixel layers are at: 51, 89 and 123 mm; the first two SCT layers are at 299 and 371 mm.
	Figure 22: Resolution for the reconstruction of the invariant mass of the charged-pion pair for K0s→π+π- decays in events containing B-hadron decays in various radial intervals (upper) and as a function of the K0s decay radius (lower).
	Figure 23: Efficiency to reconstruct charged-pion pairs for K0s→π+π- decays in events containing B-hadron decays as a function of the K0s decay radius (upper) and as a function of the |η| of the K0s (lower).

Particle Identification, Reconstruction of Electrons and Photon Conversions

	Figure 24: Probability distribution as a function of the fraction of energy lost by electrons with pT=10GeV and 25GeV (integrated over a flat distribution in η with |η|<2.5) traversing the complete inner detector.
	Figure 25: Fraction of energy lost on average by electrons with pT=25GeV as a function of |η|, when exiting the pixel, the SCT and the inner detector tracking volumes. For |η|>2.2, there is no TRT material, hence the SCT and TRT lines merge.
	Figure 26: Radial position of photon conversions in the barrel region (|η|<0.8) deduced from Monte-Carlo truth information (arbitrary normalisation).
	Figure 27: Probability for a photon to have converted as a function of radius for different values of |η|, shown for photons with pT>1GeV in minimum bias events.

Electron Reconstruction

	Figure 28: Probability distributions for the ratio of the true to reconstructed momentum (upper) and its reciprocal (lower) for electrons with pT=25GeV and |η|>1.5. The results are shown as probabilities per bin for the default Kalman fitter and for two bremsstrahlung recovery algorithms.
	Figure 29: Probability distributions for the ratio of the true to reconstructed momentum for electrons with pT=25GeV and |η|<0.8 (upper) and pT=10GeV and |η|>1.5 (lower). The results are shown as probabilities per bin for the default Kalman fitter and for two bremsstrahlung recovery algorithms.
	Figure 30: Efficiencies to reconstruct electrons as a function of |η| for electrons with pT=25GeV (upper) and pT=10GeV (lower). The results are shown for the default Kalman fitter and for two bremsstrahlung recovery algorithms.

Figure 31: Probability for the reconstructed invariant mass of electron pairs from J/ψ→ee decays in events with Bd→J/ψ(ee)K0s. Distributions are shown for both electrons with |η|<0.8 (upper) and |η|>1.5 (lower). The results are shown for the default Kalman fitter and for two bremsstrahlung recovery algorithms. The true J/ψ mass is shown by the vertical line.

Electron Identification

	Figure 32: Average probability of a high-threshold hit in the barrel TRT as a function of the Lorentz γ-factor for electrons (open squares), muons (full triangles) and pions (open circles) in the energy range 2-350GeV, as measured in the combined test-beam (CTB).
	Figure 33: Pion efficiency shown as a function of the pion energy for 90% electron efficiency, using high-threshold hits (open circles), time-over-threshold (open triangles) and their combination (full squares), as measured in the combined test-beam.
	Figure 34: Number of hits on a track as a function of |η| for a track crossing the TRT.
	Figure 35: Pion efficiency expected from simulation as a function of |η| for an efficiency of 90% or 95% for electrons with pT=25GeV.

Conversion Reconstruction

	Figure 36: Efficiency to reconstruct conversions of photons with pT=20GeV and |η|<2.1, as a function of the conversion radius (upper) and pseudorapidity (lower). Shown are the efficiencies to reconstruct single tracks from conversions, the pair of tracks from the conversion and the conversion vertex.
	Figure 37: Efficiency to identify conversions of photons with pT=20GeV and |η|<2.1, as a function of the conversion radius (upper) and pseudorapidity (lower). The overall efficiency is a combination of the efficiency to reconstruct the conversion vertex, as shown also in Fig. 36, and of that to identify single-track conversions

Responsible: StephenHaywood
Last reviewed by: Never reviewed