16 Integration of Detectors into a Large Experiment: Examples from ATLAS. . .
727
will also thus be able to identify forward jets produced in vector-boson fusion
processes.
• good separation between hadronic showers from QCD jets and those from decays
of τ -leptons.
• fast and efficient identification of the processes of interest at the various trigger
levels, in particular for the L1 trigger (see Sect. 16.6).
16.4.1.2 General Features of Electromagnetic Calorimetry
The ATLAS EM calorimeter [25] is divided into a barrel part covering approximately |η| < 1.5 and two end-caps covering 1.4 < |η| < 3.2, and its main
parameters are listed in Table 16.10. Its fiducial coverage is without appreciable
cracks, except in the transition region between the barrel and end-cap cryostats,
where the measurement accuracy is degraded over 1.37 < |η| < 1.52 because
of large energy losses in the material in front of the active EM calorimeter, which
reaches up to 6 X 0 . The excellent uniformity of coverage is a direct consequence
of the design of this lead/liquid Argon sampling calorimeter with accordion-shaped
electrodes and absorbers. The total thickness of the EM calorimeter varies from a
minimum of 24 X 0 (at η ≈ 0) to a maximum of 35 X 0 (at η ≈ 2.5). This depth is
sufficient to contain EM showers at the highest energies (a few TeV) and preserve
the energy resolution, in particular the constant term which is dominant above a few
hundred GeV.
As can be seen from Table 16.10, the ATLAS EM calorimeter has been designed
with both excellent lateral and longitudinal granularity, with samplings in depth
optimised for energy loss corrections (presampler) and for shower pointing accuracy
together with γ /π 0 and electron/jet separation (strips). The intrinsic performance of
the EM calorimeter is however significantly affected by the unavoidable amount of
material which had to be incorporated in the tracker system (see Fig. 16.10), and
also by the cryostats and the solenoid coil in the case of the ATLAS EM calorimeter
(see Sect. 16.8.2 for more details).
16.4.1.3 General Features of Hadronic Calorimetry
Figure 16.13 shows the total number of absorption lengths contained in the
ATLAS hadronic calorimetry and in front of the muon system as a function of
pseudorapidity. Good containment of jets of typically 1 TeV energy requires about
11 λ in the full calorimeter, a target which has been achieved over most of the
pseudorapidity range.
For the central part of the hadronic calorimetry, which covers the range 0 <
|η| < 1.7, the sampling medium consists of scintillator tiles and the absorber
medium is steel. The tile calorimeter is composed of three parts, one central
barrel and two extended barrels. The choice of this technology provides maximum
radial depth for the least cost for ATLAS. The hadronic calorimetry is extended to
727
will also thus be able to identify forward jets produced in vector-boson fusion
processes.
• good separation between hadronic showers from QCD jets and those from decays
of τ -leptons.
• fast and efficient identification of the processes of interest at the various trigger
levels, in particular for the L1 trigger (see Sect. 16.6).
16.4.1.2 General Features of Electromagnetic Calorimetry
The ATLAS EM calorimeter [25] is divided into a barrel part covering approximately |η| < 1.5 and two end-caps covering 1.4 < |η| < 3.2, and its main
parameters are listed in Table 16.10. Its fiducial coverage is without appreciable
cracks, except in the transition region between the barrel and end-cap cryostats,
where the measurement accuracy is degraded over 1.37 < |η| < 1.52 because
of large energy losses in the material in front of the active EM calorimeter, which
reaches up to 6 X 0 . The excellent uniformity of coverage is a direct consequence
of the design of this lead/liquid Argon sampling calorimeter with accordion-shaped
electrodes and absorbers. The total thickness of the EM calorimeter varies from a
minimum of 24 X 0 (at η ≈ 0) to a maximum of 35 X 0 (at η ≈ 2.5). This depth is
sufficient to contain EM showers at the highest energies (a few TeV) and preserve
the energy resolution, in particular the constant term which is dominant above a few
hundred GeV.
As can be seen from Table 16.10, the ATLAS EM calorimeter has been designed
with both excellent lateral and longitudinal granularity, with samplings in depth
optimised for energy loss corrections (presampler) and for shower pointing accuracy
together with γ /π 0 and electron/jet separation (strips). The intrinsic performance of
the EM calorimeter is however significantly affected by the unavoidable amount of
material which had to be incorporated in the tracker system (see Fig. 16.10), and
also by the cryostats and the solenoid coil in the case of the ATLAS EM calorimeter
(see Sect. 16.8.2 for more details).
16.4.1.3 General Features of Hadronic Calorimetry
Figure 16.13 shows the total number of absorption lengths contained in the
ATLAS hadronic calorimetry and in front of the muon system as a function of
pseudorapidity. Good containment of jets of typically 1 TeV energy requires about
11 λ in the full calorimeter, a target which has been achieved over most of the
pseudorapidity range.
For the central part of the hadronic calorimetry, which covers the range 0 <
|η| < 1.7, the sampling medium consists of scintillator tiles and the absorber
medium is steel. The tile calorimeter is composed of three parts, one central
barrel and two extended barrels. The choice of this technology provides maximum
radial depth for the least cost for ATLAS. The hadronic calorimetry is extended to