dvcs_simulation

Overview

An event generator for Deeply Virtual Compton Scattering (DVCS) simulations, supporting multiple models:

• KM15: Kumerički, Krešimir and Müller, Dieter, EPJ Web of Conferences 112, 01012 (2016), arXiv:1512.09014 [hep-ph]
• VGG: M. Vanderhaeghen, P. A. Guichon, and M. Guidal, Phys.Rev. D60, 094017 (1999), arXiv:hep-ph/9905372 [hep-ph].
• BH: pure Bethe-Heitler process

Much of the initial set up for this repository comes from Sangbaek Lee (https://gitlab.com/sangbaek/km15gen).

Installation

git clone https://github.com/tbhayward/dvcs_simulation.git
cd dvcs_simulation
chmod +x install.sh
./install.sh

Command-Line Options

Core Parameters

Option	Description	Default
--beam	Beam energy in GeV	10.604
--model	Physics model (km15, vgg, bh)	km15
--nentries	Number of events to generate	1
--fname	Output filename prefix	output

Kinematic Ranges

Option	Description	Default	Range
--xBmin	Minimum $x_B$	0.05	0.001–0.99
--xBmax	Maximum $x_B$	0.75	0.001–0.99
--Q2min	Minimum $Q^2$ (GeV²)	0.9	0.1–15
--Q2max	Maximum $Q^2$ (GeV²)	11.0	0.1–15
--tmin	Minimum $t$ (GeV²)	0.085	0.01–2.0
--tmax	Maximum $t$ (GeV²)	1.79	0.01–2.0
--ymin	Minimum $y$	0.19	0-1
--ymax	Maximum $y$	0.85	0-1
--w2min	Minimum $W^2$ (GeV²)	3.61

Advanced Options

Option	Description
--seed	Set predefined seed (0 = automatic)

... Several additional advanced options if you are willing to bravely venture deep into the dvcsgen installation.

Usage Examples

Basic KM15 Generation

python main.py --model km15 --nentries 1000 --fname km15_test

Basic VGG Generation

python main.py --model vgg --nentries 1000 --fname vgg_test

Basic BH Generation

python main.py --model bh --nentries 1000 --fname bh_test

Limited KM15 kinematic range and non-default beam energy

python main.py --model km15 --nentries 1000 --fname km15_test --Q2min 2 --Q2max 3 --beam 6.5

Output Files

• <fname>.dat: Generated events in CLAS12 Lund format.
• Automatic handling of temporary files from dvcsgen.

Dependencies

• Python 3.6+
• Cython
• NumPy
• SciPy
• Gepard (for VGG/BH models)
• CLAS12 environment (via module load clas12)

Troubleshooting

Q: Getting test.1.dat instead of test.dat?
A: The code automatically renames files. Temporary files from dvcsgen will be cleaned up.

Q: Installation fails with Cython errors?
A: Ensure you have Cython installed:

pip3 install --user cython

Q: dvcsgen not found?
A: Run source ~/.bashrc after installation and/or verify that the CLASDVCS_PDF environment variable is set.

plot_kinematics.py

Description:
plot_kinematics.py is a utility script to visualize and analyze the kinematics of the generated DVCS events. It reads the output Lund file (e.g., *.dat) generated by this event generator and produces a set of histograms for electron, proton and photon momenta, as well as common DIS variables such as y, Q², W, x_B, and t.

Usage Examples:
To plot a single file:

python plot_kinematics.py myevents.dat --beam-energy 10.2

Here, myevents.dat is the Lund-format file to analyze, and --beam-energy (or -b) can be used to specify a beam energy different from the default of 10.604 GeV.

To plot two files with custom legend labels:

python plot_kinematics.py file1.dat file2.dat -b 10.604 -l "Model A" "Model B"

To plot three files with custom legend labels:

python plot_kinematics.py file1.dat file2.dat file3.dat -l "Set 1" "Set 2" "Set 3"