DISPLIT Project
Goal : Investigate hadrons internal structure through the multiplicity distribution of gluons in high-energy scatterings of hadrons.
Using Monte-Carlo simulations in C++/ROOT
Install and configure ROOT framework
ROOT is a C++ framework for large scale data analysis developed at CERN. See https://root.cern.ch/.
The CMakeLists.txt file assumes you have defined an environment variable called
$ROOTSYS pointing to your ROOT installation directory.
For instance you could add these lines in your ~/.bashrc file:
export ROOTSYS=/usr/local
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ROOTSYS/lib
Compile and run
You will also need MPI libraries to compile displit. For example on Ubuntu run :
$ sudo apt-get install libopenmpi-dev
Go then to displit root directory and type :
$ mkdir build
$ cd build
$ cmake ..
$ make
$ ./main [options]
To run displit, either use ./main [options] or if using MPI
(only with options generate-mpi and fluctuations-mpi)
use mpiexec -np $NB_TASKS ./main [options].
Options
Warning : filenames are used to get/set parameters. Do not change it.
Generation of events and histograms
generate [nb_events] [delta] [max_y] [cutoff_type]
Generate nb_events events with UV cutoff delta, maximal rapidity max_y and
an IR cutoff type cutoff_type. Each event is stored as a TTree in a ROOT file.
You can stop it with Ctrl-C and events generated until this point will be saved.
generate-mpi [parameters file]
Example of parameters file :
1000000 0.01 3.00 gaussian
1000000 0.01 3.00 lorentzian1
The pattern for each line is nb_events delta max_y cutoff_type where delta
is the UV cutoff and cutoff_type is the IR cutoff.
fluctuations [filename]
fluctuations-mpi [file]
Example of files list (1 filename per line) :
mpi_tree_100000events_cutoff0.010000_ymax2.000000_gaussian.root
mpi_tree_100000events_cutoff0.010000_ymax2.000000_lorentzian1.root
generate-fluctuations-mpi [parameters file]
Example of parameters file :
100 10000 0.01 3.00 2.0 gaussian
100 10000 0.01 3.00 2.0 lorentzian1
The pattern for each line is nb_tasks nb_events_per_task delta max_y R cutoff_type.
Plots and graphics
draw-fluctuations [histogram file] [max_y]
Draw the distribution of probability of having n dipoles (fluctuations) after an evolution until
rapidity max_y.
compare [histofile]
Draw the fluctuations for different histograms on the same canvas.
compare-c [histofile] [mode]
Draw the value of c for different values of parameter mode which can be r,
delta or ymax. The histograms filenames are in histofile. All parameters
other than mode should be fixed.
compare-R [histofile]
Test the fluctuations dependance in x_{01}/R.
Miscellaneous
list-cutoffs
List available IR cutoffs.
draw-cutoffs
Draw some IR cutoffs (not all of them).
check [tree_file]
Check the real number of events recorded in [tree_file] against the theoretical number (encoded in the filename).
fit-bare-r [delta] [max_y]
Draw the distribution of dipoles size for given parameters : UV cutoff delta and
maximal rapidity max_y, comparing with and without an IR cutoff (rigid).
ancestors [nb_events] [rho] [max_y]
Not fully tested yet.
Running displit with SLURM + MPI
The file generic.slurm is provided as an example to launch displit on a cluster
using SLURM and OpenMP.
References
[1] T. Liou, A.H. Mueller, S. Munier. Fluctuations of the multiplicity of produced particles in proton-nucleus collisions. 2016
[2] G.P. Salam. OEDIPUS: Onium evolution, dipole interaction and perturbative unitarization simulation. Comput.Phys.Commun. 105 (1997) 62-76.