Gabriele Cosmo
60 lines
3.0 KiB
Plaintext
60 lines
3.0 KiB
Plaintext
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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Example ch3
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A. Sytov
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INFN Ferrara Division, sytov@fe.infn.it
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INTRODUCTION
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Example ch3 demonstrates the minimum requirements necessary to integrate the
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G4CoherentPairProduction process into a project, along with the G4ChannelingFastSimModel
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and G4BaierKatkov models, to simulate the physics of electromagnetic showers in
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an oriented crystal.
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The key concept is the acceleration of electromagnetic processes (both radiation and
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pair production) in an oriented crystal, which can significantly reduce the effective
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radiation length [1,2]. Potential applications include electron/positron sources for
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accelerator experiments, as well as crystalline oriented calorimeters for collider and
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space applications [1,2].
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This example serves as a guideline for users on how to add this physics
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to their existing Geant4 projects. It includes the minimum necessary options
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to incorporate this physics. Specifically, it requires registering
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G4FastSimulationPhysics and G4CoherentPairProductionPhysics in the main routine and
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adding a few lines of code in DetectorConstruction.
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All of this physics does not depend on the physics list. In particular, the
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process G4CoherentPairProduction simulates only coherent part of pair production in
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the crystal volume, while the incoherent one should be simulated with
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standard Geant4 processes.
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DESCRIPTION
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The example simulates high energy photon interaction (typically above 10 GeV) with
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an oriented W crystal with <111> crystal axes aligned along the photon beam direction.
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The structure of this example is very similar to the example ch1.
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ch3 includes a straight W crystal and a detector positioned behind it.
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The incoming photon beam is set up in macro run.mac.
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One can also use the Geant4 GUI by launching the code without specifying a macro file.
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In this case, the visualization setup is automatically loaded through the vis.mac and
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init_vis.mac macro files. The initial beam distribution in this setup will be identical
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to that in run.mac.
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The example does not include any input of the model or geometry parameters
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from the macro to keep it as straightforward as possible. The output is recorded
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into the file results.root. It consists of the spectrums of e-, e+
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and gamma arriving to the detector. To build these plots, one has to
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open this file in root and use Spectrum_electrons->Draw(), Spectrum_positrons->Draw()
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and Spectrum_gamma->Draw() for e-, e+ and gamma, respectively.
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REFERENCES
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[1] V. N. Baier, V. M. Katkov, V. M. Strakhovenko, Electromagnetic Processes
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at High Energies in Oriented Single Crystals (World Scientific, Singapore, 1998).
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[2] L. Bandiera, V.V. Tikhomirov et al. Phys. Rev. Lett. 121, 021603 (2018).
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