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 (ATLCOMPHYS2008105)
 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,
CERNOPEN2008020, 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: Cutaway view of the ATLAS inner detector.


Figure 2: Plan view of a quartersection of the ATLAS inner detector showing each of the major elements with its active dimensions.




Figure 3: Material distribution (X_{0}, 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 subdetectors, 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 p_{T}=1, 5 and 100GeV.
Transverse momentum (lower), at which the multiplescattering 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 p_{T}=1, 5 and 100GeV.
Transverse momentum (lower), at which the multiplescattering 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 p_{T}=1, 5 and 100GeV.
Transverse momentum (lower), at which the multiplescattering contribution
equals the intrinsic resolution,
as a function of η.


Figure 7: Resolution of the transverse impact parameter, d_{0} (left) and the
modified longitudinal impact parameter, z_{0} 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 highenergy muons (μ^{}) (left) and electrons (e^{}) (right) for
p_{T}=0.5TeV (top) and p_{T}=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 highenergy muons and electrons as a
function of p_{T} for particles with η<2.5 (upper) and as a
function of η for p_{T}=2TeV (lower).

Track reconstruction Efficiency



Figure 11: Track reconstruction efficiencies as a function of η for
muons (upper) and pions (lower) with p_{T}=1,5 and 100GeV.


Figure 12: Track reconstruction efficiencies as a function of η for
electrons with p_{T}=1,5 and 100GeV.


Figure 13: Track reconstruction efficiencies as a function of η for
muons, pions and electrons
with p_{T}=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{Δη^{2}+Δφ^{2}})
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 p_{T} for η<2.5
and p_{T}>0.1GeV
(upper) and as a function of η for two different p_{T} ranges (lower) in
minimum bias events (nondiffractive inelastic events).




Figure 17: Rate of candidate
fake tracks as a function of p_{T} for η< 2.5 and p_{T}> 0.1GeV
(upper) and as a function of η (lower) in
minimum bias events (nondiffractive 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 MonteCarlo 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 topquark pairs
and Hγγ decays with m_{HM}=120GeV. The results are shown without pileup 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 Bhadron 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 threeprong hadronic
τdecays 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 τleptons have an average transverse momentum of 36GeV.




Figure 21: Resolution for the reconstructed radial position of the secondary
vertex for K^{0}_{s}→π^{+}π^{} decays
in events containing Bhadron decays in various radial intervals (upper)
and as a function of the K^{0}_{s} 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
chargedpion pair for K^{0}_{s}→π^{+}π^{} decays
in events containing Bhadron decays in various radial intervals (upper)
and as a function of the K^{0}_{s} decay radius (lower).




Figure 23: Efficiency to reconstruct
chargedpion pairs for K^{0}_{s}→π^{+}π^{} decays
in events containing Bhadron decays
as a function of the K^{0}_{s} decay radius (upper)
and as a function of the η of the K^{0}_{s} (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 p_{T}=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 p_{T}=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
MonteCarlo 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 p_{T}>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 p_{T}=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 p_{T}=25GeV and η<0.8 (upper)
and p_{T}=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 p_{T}=25GeV (upper) and p_{T}=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 B_{d}→J/ψ(ee)K^{0}_{s}.
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 highthreshold hit in the barrel TRT as
a function of the Lorentz
γfactor for electrons (open squares), muons (full
triangles) and pions (open circles)
in the energy range 2350GeV, as measured in the combined
testbeam (CTB).


Figure 33: Pion efficiency shown as a function of the pion energy for
90% electron efficiency, using highthreshold
hits (open circles), timeoverthreshold (open triangles) and
their combination (full squares),
as measured in the combined testbeam.


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 p_{T}=25GeV.

Conversion Reconstruction



Figure 36: Efficiency to reconstruct conversions of photons with p_{T}=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 p_{T}=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 singletrack conversions

Major updates:

StephenHaywood  18 Dec 2008
Responsible: StephenHaywood
Last reviewed by: Never reviewed