Detailed simulation of Forward Calorimeter Layer 1

• Author: Zhaoyuan "Maxwell" Cui
• Advisor: Prof. Erich Varnes
• Physics Department, University of Arizona
• This is an undergraduate directed research

Introduction

Forward Calorimeter (FCal) is one of the detectors in the ATLAS experiment located at Large Hadron Collider (LHC) CERN. The first layer of FCal (FCal1) is a EM calorimeter. Due to the large |η|, FCal1 is important in determining the location of the vertex of large pseudorapidity electrons and positrons. The goal of the study is to use GEANT4 to simulate the FCal1 detector and the detecting process. By using the data from the simulation, the timing resolution of FCal1 can be calculated. For a detail description of the simulation, please look at the report Studying the timing resolution of FCal1 with a detailed simulation using Geant4.pdf

Before compiling

GEANT4 uses CMake to generate Makefile. Therefore, a CMakeLists and the propriate paths of files are important. The flags for cmake may vary on different machine and also under differnet circumstances of desired results.

Compile

In the directory of CMakeLists.txt, create a new directory called build:

mkdir build

Then change directory to the build directory:

cd build

Source Geant4 and invoke cmake:

source /PathToGeant4/bin/geant4.sh
cmake -DGeant4_DIR=/PathToGeant4/lib/Geant4-x.x.x ..

where the x's stand for the version of the Geant4.

A Makefile should be generated after the cmake process, to compile the program, type:

make 

or, if cpu has more than one core, one can use multiple cores to accelerate the compile process. Type:

make -jn

where n is the number of cores that the user want to use.

Running program

After compiling the program, one can now run the program. Look for the executable in the build director. In the default CMakeLists.txt, macro files are copied to the build directory after successfully invoking cmake. In the default setup of the program, running the program leads to the interactive mode of Geant4, which is a GUI that will draw the geometry of the detector. In a detailed simulation, this can take significant amount of time and may lead to internal error if memory is not enough for the graphic drawing. For this reason, batch mode is recommended for collision simulation. Intercative mode can be skipped by executing the program with macro file in an actual simulaton. Nevertheless, in the phase of building the geometry of the detector, interactive mode is useful as it visiually shows the simulated geometry of the detector and can aid the user to create the desired geometry.

Notes

Please note that Geant4 is highly customizable tool kit. User should design and/or modify the code to meet his or her own concern. Most parts, especially the action and the macro files, are therefore subject to change.