Event generator for Deep Exclusive Meson Production.
To build the event generator, the compiler needs acces to both a compiled installation of CERN ROOT and its source code. ROOT version 6.08.06 or later is supported, and must be installed with the MathMore package enabled. Be sure not to change the location of either the ROOT source or compiled files after installation, as this will interfere with ROOT's built in CMake configurators.
CMake is also required. CMake 2.8 is the minimum supported version, and CMake 3 has been tested as well.
After downloading the source create a build directory and cd to it. Take note of the location of the source directory (where CMakeLists.txt should be stored) and run the commands:
As a one liner -
The event generator can now be run using the following command in the data/ directory.
Building on the JLab iFarm requires you to set up some software versions beforehand, to build successfully, I did the following -
I then build DEMGen using the one liner above without any issues, you will need to load these modules when running the generator subsequently (this is done by default in the farm job scripts)
The files within the top level directory and the directory structure of the generator are outlined below. Note that files within subdirectories are not outlined in full. Please refer to comments within each source/header files and README files within subdirectories (where applicable) for details on individual files within subdirectories.
.json config file based upon inputs and runs DEMPgen with produced configuration file. See file comments and description below for details on usage..json config file based upon inputs and runs DEMPgen with produced configuration file. This version is configured for use on the JLab iFarm system. See file comments and description below for details on usage..json config file for EIC event generation. Used by shell scripts below. See comments within file for details on flags..json config file for SoLID event generation. See comments within file for details on flags..json file with all configuration options to gereate a test EIC event sample. See reference_README.md within the reference_output directory for details..json files associated with the header files for the SoLID module.reference_README.md file within this directory.Instructions for a comprehensive test run, and a reference file to compare to (using for example, diff) are included in -
The file Config_EIC.json and Config_SoLID.json contain all the configuration options for EIC and SoLID event generation respectively. Use these as a template for other configuration files, which may be given as an argument to the event generator.
The EIC module of DEMPgen has two different calculation methods that may be used to calculate the ejectile properties.
These are referred to as the "Analytical" and "Solve" methods. Either can be used in a simulation run, just change the config file to switch between them.
In your config .json file, select between the two versions using the "calc_method" argument, this can be set to Analytical or Solve, e.g.
If you are using the shell scripts provided to run a lot of simulations, modify Config_EIC.json BEFORE running the shell scripts.
The event data is output to the configured file location relative to the build directory. The TTree in this file contains all kinematic data for all particles in the laboratory rest frame. Variables with the prefix "Vert" represent values read at the interaction vertex. Values with the prefix "Lab" represent values read after all correcting effects (multiple scattering, ionization, etc.) have been applied.
The Particle class inherits from the root TLorentzVector class so that its functions are immediately accessible through the Particle objects. It's member variables include its mass, charge, and its GEMC compatible id.
The Event class contains all particles of a single event, in one frame of reference. It includes methods enabling transformation to other frames of reference and coordinate systems.
The Asymmetry class calculates asymmetry amplitudes based on Monte-Carlo data by Goloskokov and Kroll. The asymmetry objects are persistent between events.
A class to hold various distribution functions for randomly generated variables, such as scattered electron energy. These functions should be persistent between events, and will provide fast random numbers.
Stores the kinematic ranges for the scattered electron and generates them with random energy and direction within the range, using sphere point picking.
Generates the target neutron with Fermi momentum (when enabled) and proton for FSI (when enabled, may also have Fermi momentum).
This class reads in the kinematic variables for the incident, target, and scattered particles and uses conservation laws to solve for the remaining two particles. The pion is first given a random direction. A fast root finding algorithm then calculates the pion's momentum magnitude, which is then used to find the proton's momentum. Pion direction may also be passed as an argument for debugging purposes.
This class returns the cross sections and weights for the event. It acts as an interface between the current version of the event generator and header files from the old event generator (seen under branch "original"), which contain the parameterization of the cross sections.
Manages the ROOT TTree object to be stored in the output .root file. Contains methods to easily add all kinematics data stored in a particle or DEMPEvent object.
Transforms particle kinematics based on three effects caused by transition through matter: Ionization, Bremsstrahlung, and Multiple Scattering.
Computes the effect of final state interaction between the produced pion and one of the two protons of the target nucleus. The momentum of the outgoing pion and recoiled proton, as well as the cross section of the interaction is calculated based on elastic pion-nucleon scattering.
This project uses JsonCpp to read in configuration options. The amalgamated sources for JsonCpp are redistributed with this project in compliance with the MIT license.
!!! NOTICE !!!
This script copies Config_EIC.json and formats a new file based upon this, DO NOT MODIFY Config_EIC.json (other than the calculation method) if you want to use this script!
!!! NOTICE !!!
To facilitate the submission of batch jobs, I created a csh script to automatically construct .json config files and run them. This script can also be utilised to run the generator manually, without the need to go and edit a json file.
The script requires 8 arguments (which is a lot, I know), but in the K+ case, it expects 9. They are as follows -
So as an example if you executed the following -
You would run the generator for 18 GeV e- on 275 protons for ip6, throwing 100000 events with the K+/Lambda generator.
This script creates and submits batch jobs. It is designed for use with the torque queueing system on Lark at the University of Regina. The jobs the script creates and submits all execute the Process_EIC.csh script described above. This script requries a very similar set of arguments -
The script automatically generates a random seed itself using the /dev/urandom function.
DEMPgen is licensed under the GNU General Public License v3.0.