7.2 Calorimeters (Calo)

Control of the attributes of data from the various calorimeters is described in:

7.2.1 Liquid Argon Electromagnetic Calorimeter (LAr)

The Liquid Argon Electromagnetic Calorimeter consists of a barrel and two endcaps. The barrel inner and outer radii are 150 and 198 cm, respectively. The end caps start at 315 and end at 450 cm. Each of the barrel and two end caps are made up from four samplings with separate readout. The first sampling (sampling 0) is called the presampler. Each of the four samplings is split in a large number of separate measuring cells in φ and in η. The cell geometry is projective in φ and η. The thickness of the different samplings varies with η in order to make the thickness of the two middle samplings to be a roughly constant number of radiation lengths.

A detailed description of the parameters which are common to all calorimeters may be found at 7.2.11 Calorimeter Attributes.

The granularity Δη×Δφ of the LAr varies over a large range depending on the sampling and pseudorapidity:

Table 7.1. Granularity of LAr

 Barrel Endcap 
SamplingΔη×Δφ|η| rangeΔη×Δφ|η| range
0 (pre)0.025×0.1|η|<1.520.025×0.11.5<|η|<1.8
10.003×0.1|η|<1.4750.025×0.11.375<|η|<1.5
   0.003×0.11.5<|η|<1.8
   0.004×0.11.8<|η|<2.0
   0.006×0.12.0<|η|<2.5
   0.1×0.12.5<|η|<3.2
20.025×0.025|η|<1.4750.025×0.0251.375<|η|<2.5
   0.1×0.12.5<|η|<3.2
30.05×0.025|η|<1.4750.05×0.0251.5<|η|<2.5

7.2.2 Tile Calorimeter (TILE)

The TILE calorimeter is a sampling calorimeter using iron as the absorber and scintillating tiles as the active material. It is used to measure the hadronic energy of particles moving at small pseudorapidities. The total η coverage of the TILE is |η|<1.7. The TILE is split mechanically into three parts: barrel and left and right extended barrels. The barrel region has a pseudorapidity coverage of |η|<1.0. The extended barrel region covers the pseudorapidity range 0.8<|η|<1.7. The inner radius of the calorimeter is 2.28 m and the outer radius is 4.25 m. It is longitudinally segmented into three samplings. The cells are arranged in a pseudo-projective geometry with a granularity of 0.1×0.1 in Δη×Δφ for the inner two samplings and 0.2×0.1 in Δη×Δφ for the outer sampling.

A detailed description of the parameters which are common to all calorimeters may be found at 7.2.11 Calorimeter Attributes.

7.2.3 Hadronic Endcap Calorimeter (HEC)

The HEC is a liquid argon based hadronic endcap calorimeter. It is used to measure the hadronic energy of particles in the pseudorapidity range 1.5<|η|<3.2. Each endcap consists of two independent wheels which are longitudinally segmented into four samplings. The cell geometry is fully projective in azimuth and pseudo-projective in pseudorapidity with a granularity of 0.1×0.1 in Δη×Δφ in the pseudorapidity range 1.5<|η|<2.5 and 0.2×0.2 in Δη×Δφ in the pseudorapidity range 2.5<|η|<3.2.

A detailed description of the parameters which are common to all calorimeters may be found at 7.2.11 Calorimeter Attributes.

7.2.4 Forward Calorimeter (FCAL)

The FCAL is a liquid argon based calorimeter providing coverage in the pseudorapidity range 3.2 < |η| < 4.9. It is longitudinally segmented into three samplings. The innermost sampling uses copper as the absorbing material and is primarily used to measure electromagnetic energy. The outer two samplings use tungsten as the absorbing material and are used to measure hadronic energy. The cells have a granularity of 0.2×0.2 in Δη×Δφ. The FCAL is situated at a distance in Z of between 4.7 and 6.1 m from the interaction point and at a radial distance between 7 and 46 cm from the beam axis.

A detailed description of the parameters which are common to all calorimeters may be found at 7.2.11 Calorimeter Attributes.

7.2.5 Clusters (Cluster)

Clusters are formed from energy deposits in the cells of the liquid argon calorimeter ( 7.2.1 Liquid Argon Electromagnetic Calorimeter (LAr)). Clusters may not currently be viewed, however, cells in the liquid argon calorimeter may be colored according to their associated cluster.

The color of each cluster is defined by the color function which may be either

  • constant, in which case the constant color is used for all clusters,

or it may vary with each cluster being given the color of its

  • index: in the range 0 to numClusters-1,

  • associated E/Gamma reconstucted object.

7.2.6 Simulated Neutral Particles in Calorimeter, Neutral Truth (SNP)

To be filled!

7.2.7 Regions Of Interest (EmTauROI)

Regions of interest are Δφ×Δη regions of solid angle defined by the trigger system. They may be viewed in the φ/η ( 5.2 φ/η Projection) projection and the Lego Plot ( 5.11 Lego Plot).

The color of each ROI is defined by the color function which may be either

  • constant, in which case the constant color is used for all ROI's,

or it may vary with each ROI being given the color of its

  • index: in the range 0 to numROI-1.

More information about colors in Atlantis is given in 7.6.1 About the Use of Colors.

7.2.8 Jet Region of Interest (JetROI)

7.2.9 Level-1 Calorimeter Trigger Input Data: E/Gamma, tau/had (LVL1TriggerTower)

The data of reduced granularity used inside the Level-1 Calorimeter Trigger system can be displayed in the Lego Plot ( 5.11 Lego Plot). The switch "View" allows to select "LVL1TriggerTower" and "LVL1JetElement". The first set is used inside the E/Gamma and tau/had trigger, the second is the jet and energysum trigger. The granularity displayed matched the real system.

The color of each Trigger data is defined by the color function which can only be constant, and the constant color is used for all Trigger data.

More information about colors in Atlantis is given in 7.6.1 About the Use of Colors.

7.2.10 Level-1 Calorimeter Trigger Input Data: jet, ET-Miss/ET-Sum (LVL1JetElement)

To be filled!

7.2.11 Calorimeter Attributes

Available Projections

In Atlantis, the calorimeters (LAr ( 7.2.1 Liquid Argon Electromagnetic Calorimeter (LAr)), TILE ( 7.2.2 Tile Calorimeter (TILE)), HEC ( 7.2.3 Hadronic Endcap Calorimeter (HEC)), FCAL ( 7.2.4 Forward Calorimeter (FCAL))) can be seen in the following projections:

Table 7.2. Projections and calorimeters

ProjectionCalorimeter
Y/X ( 5.1 Y/X Projection)LAr barrel, TILE barrel and extended barrel
ρ/Z ( 5.4 ρ/Z Projection)LAr barrel and endcap, TILE, HEC and FCAL
φ/ρ ( 5.5 φ/ρ Projection)LAr barrel, TILE barrel and extended barrel
φ/Z ( 5.6 φ/Z Projection)LAr endcap and HEC
φ/η ( 5.2 φ/η Projection)LAr, TILE, HEC, FCAL

Cells

To display only the calorimeter histograms without the calorimeter cells the cells must be switched off via the Cells parameter.

Energy Representation

The energy deposited in a calorimeter cell is represented by a polygon whose area is proportional to the energy in that cell. The process of generating such a polygon is:

  • Calculate the real shape of the cell.

  • Get the centroid of the cell.

  • Scale the cell with respect to the centroid according to the energy density in the cell.

The scaling according to energy density (calibration) can be done in different ways according to the Energy Calibration parameter:

  • Overall calibration - a single calibration for all the calorimeters. Allows to compare energy deposition in different calorimeters.

  • By Energy Type calibration - two independent calibrations for electromagnetic and hadronic energies.

  • By calorimeter calibration - a separate calibration for each calorimeter.

Additionally, the user can change the default calibration by switching on the E/S parameter and specifying for each calorimeter independently a different value of energy density than that automatically calculated by the program. The value of energy density calculated automatically corresponds to that which would completely fill the geometrical area of the cell with the highest density.

Overlapping Cells

In some projections the cells of the same calorimeter may be overlaid on top of each other. In this case the user has two options in displaying them according to the Energy Mode parameter:

  • Display the energy Sum - the energy displayed is the sum of that in all the overlapping cells.

  • Display the energy Maximum - the maximum energy cell of all the overlapping cells is calculated and displayed.

Coloring Schemes

The scaled-by-energy-density cells can be colored in different ways according to the Color Function parameter:

  • Constant - a single color is used, which is given by the Constant parameter.

  • Sub Detector - the cells are colored by the sub detector in which they are.

  • Cluster - coloring by energy cluster which comes with data. If the cell does not belong to any cluster it is colored using the color defined by Unconnected parameter.

  • Sampling - coloring by the sampling(layer) in which the cell is.

  • Jet - coloring by the jet to which the cell is associated.

Cell Frames and Geometry

Each cell may have a frame which is drawn on the boundary of the cells polygon. The color and the width of this frame can be given by setting the Frame and Frame Width parameters. Whether the frame is drawn or not is controlled by the state of the Frame parameter.

In some cases it may be useful to see not only the scaled cells but also the initial (real) cells. This can be obtained by switching on the Cell Geometry parameter. The background color used to draw the cell geometry is given by the value of the same parameter.

Histograms

Another possibility to represent the energy deposition in the calorimeters is by Histograms. Where appropriate the energy deposition is summed over layers and depth. A histogram can be obtained by switching on the Histogram parameter. The histogram can get different colors according to the value of the Histogram parameter. They can also have a frame with a color given by the Histo Frame parameter.

The energy is represented as the length of the histogram tower. The energy to length mapping can be customized by changing the value of Histo Scale parameter.