| 1 | |
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| 2 | ============================================================== |
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| 3 | Geant4 - an Object-oriented Toolkit for Simulation HEP |
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| 4 | ============================================================== |
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| 5 | |
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| 6 | Rich Detector for LHCb |
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| 7 | ---------------------------------- |
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| 8 | |
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| 9 | This example is intended to simulate the TestBeam Setup of the Rich detector |
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| 10 | at the LHCb to test the performance of the aerogel radiator. |
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| 11 | The goal of the Rich is the proper identification of charged particles |
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| 12 | in a momentum range of 1-150 GeV/c and to assist in the separation of |
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| 13 | signal and background. |
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| 14 | |
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| 15 | |
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| 16 | 1. GEOMETRY DEFINITION |
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| 17 | ----------------------------- |
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| 18 | |
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| 19 | It consists on 2 detector; RICH1, RICH2 which have to cover |
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| 20 | the full LHCb momentum range: |
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| 21 | |
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| 22 | RICH1: Aerogel 2 to 10 GeV/c |
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| 23 | C4F10 < 70 GeV/c |
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| 24 | |
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| 25 | RICH2: CF4 < 150 GeV/c |
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| 26 | |
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| 27 | |
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| 28 | The geometry (defined inside RichDetectorConstruction class) consists of |
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| 29 | 4 Hpd, a target containing the aerogel and a spherical mirror. |
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| 30 | The TestbeamSetUp is related to changes in teils, distances between elements |
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| 31 | of the testbeam and types. All the possible configurations are considered |
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| 32 | by a loop inside the MaterialParameters class. |
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| 33 | |
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| 34 | |
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| 35 | 2. AN EVENT: THE PRIMARY GENERATOR |
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| 36 | ------------------------------------- |
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| 37 | |
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| 38 | The primary kinematic consists of a single charge particle (normally pions) |
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| 39 | which is sent towards the target producing a rain of photons reflected and |
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| 40 | focused by the spherical mirrors and recolected after in the Hpd. |
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| 41 | |
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| 42 | The aim of the testbeam is to perform resolutions measurements with |
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| 43 | and without the aerogel to probe the improvement of its use. Comparisons |
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| 44 | between simulation and data are performed to determine the angle defined |
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| 45 | between the simmetry axis of the system (axis z) and the distance to the |
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| 46 | interaction point of the produced photons in the Hpd. |
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| 47 | |
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| 48 | The information related to type of particles to be sent, their energy |
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| 49 | and directions is included inside the PrimaryGeneratorAction class. |
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| 50 | These parameters can be changed interactively using an extern macro |
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| 51 | (run1.mac). It is recomended the use of such macro for changes because |
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| 52 | it avoids further compilations. |
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| 53 | |
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| 54 | A RUN is a set of events. |
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| 55 | |
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| 56 | |
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| 57 | 3. VISUALIZATION |
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| 58 | -------------------- |
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| 59 | |
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| 60 | The Visualization manager is set in the main(). |
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| 61 | The Initialisation of the drawing is already defined in run1.mac. |
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| 62 | The example is prepared to use any other visualization packages which |
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| 63 | can be defined in such macro or inside RichTbVis0.mac. Before running |
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| 64 | the events, the visualization must be initialized by: |
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| 65 | |
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| 66 | > /control/execute/RichTbVis0.mac |
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| 67 | |
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| 68 | The detector has longitudinal view of the geometry as default. |
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| 69 | |
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| 70 | The tracks are drawn at the end of event, and erased at the end of the run. |
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| 71 | |
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| 72 | |
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| 73 | 4. PHYSICS DEMO |
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| 74 | ---------------- |
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| 75 | |
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| 76 | The particles type and physics processes which will be available in |
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| 77 | this example are set in PhysicsList class. |
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| 78 | |
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| 79 | In addition a built-in interactive command (process/inactivate proname) |
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| 80 | allows to activate/inactivatethe processes one by one. |
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| 81 | |
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| 82 | 5. HOW TO START? |
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| 83 | ----------------- |
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| 84 | |
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| 85 | - compile and link to generate an executable |
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| 86 | % cd geant4/examples/advanced/Rich/ |
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| 87 | % gmake |
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| 88 | |
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| 89 | - execute the program in 'batch' mode from macro files |
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| 90 | % RichTbSim run1.mac |
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| 91 | |
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| 92 | - execute tests in 'interactive mode' |
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| 93 | % RichTbSim |
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| 94 | ..... |
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| 95 | |
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| 96 | Idle> type your commands |
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| 97 | ..... |
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| 98 | Idle> exit |
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| 99 | |
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| 100 | |
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| 101 | 6. HISTOGRAMS |
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| 102 | --------------- |
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| 103 | |
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| 104 | This example produces 7 histograms (saved as rich.his generated automatically |
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| 105 | during the running time) which illustrate the final state of the most important |
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| 106 | information of the example: |
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| 107 | |
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| 108 | histo1 --> Number of Photon Hits per Track |
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| 109 | histo2 --> Number of Photons before Mirror |
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| 110 | histo3 --> WaveLength of Photons before Mirror |
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| 111 | histo4 --> WaveLength of Photons after Mirror |
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| 112 | histo5 --> Cherekov Angle at roduction all angles |
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| 113 | histo6 --> Z of the Photon Emission Point |
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| 114 | histo7 --> Cherenkov Ring Radius |
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| 115 | |
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| 116 | See their definition on AnalysisManager. |
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| 117 | |
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| 118 | Note that histograms are disabled via the flag G4ANALYSIS_USE in GNUmakefile. |
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| 119 | |
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| 120 | |
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| 121 | 7. Using the PI implementation of the AIDA histograms: |
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| 122 | ------------------------------------------------------ |
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| 123 | |
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| 124 | In order to setup the proper environmental variables, needed for |
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| 125 | running AIDA / PI , run the script: |
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| 126 | |
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| 127 | --- For c-shell : source setupAidaPi.csh |
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| 128 | |
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| 129 | --- For bash-shell : . setupAidaPi.sh |
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| 130 | |
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| 131 | Notice that you need g++ 3.2 or 3.23. |
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| 132 | |
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