MCDijet

A Monte Carlo implementation to probe the distribution of linearly polarized gluons and elliptic azimuthal anisotropy in DIS dijet production at high energy

Dependencies

• g++ and gcc or compatible compiler

• GNU Scientific library

  On Linux Debian-based platforms run

   sudo apt-get install gsl-bin libgsl0-dev 
  

  On OS X with Homebrew run

   brew install gsl 
  

• Boost libraries might be required for older versions of g++

  On Linux Debian-based platforms run

   sudo apt-get install libboost-random-dev libboost-math-dev  
  

  On OS X with Homebrew run

   brew install boost 
  

• cmake V3.3.2 or higher

  On Linux Debian-based platforms run

   sudo apt-get install cmake 
  

  On OS X with Homebrew run

   brew install cmake
  

Compiling

• Adjust paths if required in Makefile

• Run

   make
  

Running

This section provides a brief description of the output of McDijet and how to work with it. To understand the calculations performed by the code we strongly recommend to read arXiv:1809.02615

• By default the flag PRINT_PARTONS, see mc_dijet.cpp, is set and the output refers to the momenta of the produced quark and anti-quark. The code also prints the virtuality of the photon etc. The order is specified in the 5th line of the output file. Every line after that corresponds to a particular gamma* + A --> q + qbar event.

  In particular:

  • pol: photon polarization (0=transverse, 1=longitudinal)
  • xS is the differential cross section at the given Q2, W, Pt, qt, z, phi, for the given photon polarization
  • phiT is the azimuthal angle of Pt
  • phiT + phi is the azimuthal angle of qt

• Run

   ./mc_dijet.x > output.dat
  

  By default 30 000 events will be produced and stored in the file output.dat.

• If you would like to directly plot this output then you would probably want to remove header and "Events processed ..." lines first:

   sed -i -e 1,5d output.dat
   sed -i -n '/Events/d' output.dat
  

  (this edits the file in place, make a backup first to preserve the original version)

Pythia as an AfterBurner

You can use Pythia8 to produce paticle showers from the two genrated partons. For this you have to

• Download Pythia 8 from http://home.thep.lu.se/~torbjorn/pythia8/pythia8235.tgz
• Extract it to the same folder, where McDijet folder is; that is "pythia8255" and "McDijet" should be located in the same folder
• Configure and compile Pythia: ./configure; make
• Uncomment line 33 in mcdijet.cpp: #include "PythiaAfterBurner.h"
• Comment line 944 in mcdijet.cpp: AfterBurner * afterBurner = new NoBurner;
• Uncomment line 945 in mcdijet.cpp: AfterBurner * afterBurner = new PythiaAfterBurner;
• Run make pythiaAfterBurner; it will produce the executable mcdijet.x
• The events are not saved in a file; instead you might consider adding your analysis routins to PythiaAfterBurner.cpp, see line 183

Reporting bugs

Please report bugs directly to [email protected]

License

Code is under the GNU General Public License. Please cite http://inspirehep.net/record/1693295 if used