Helac-Phegas: installation, production, parton-level analysis, PYTHIA shower, hadron level analysis, all standalone.

How to install Helac-Phegas

You will need a fortran compiler: gfortran or g95. Though it can run standalone, it is useful to install LHAPDF as well.

See instructions here.

Download the package from http://helac-phegas.web.cern.ch/helac-phegas/helac-phegas.html

Unpack and follow the instructions of the README to set the parameters of the myenv file.

How to run Helac-Phegas

Edit the user.inp file, to declare the process, set all the values that you want for the process, coupling constants, masses, kinematical cuts, etc...

Use the default.inp as an example.

When you are done editing, you are ready to run:

./run.sh user.inp

A new folder is created, named by the name you give in the user.inp file. (Remember everytime you run to change the name of the folder,or else it is overwritten)

Inside the folder, you find a .gzip, you unzip it, and there you have the LesHouches file (.lhe). The cross section is inside the folder named 2 , in the file output.

Store the Helac .lhe into Ntuples

So we want to store the info from the .lhe file, in order to do the analysis. Use this code


And you have the Ntuple, generated by helac, ready for analysis.

Store the PYTHIA file into Ntuples

In order to perform the parton shower, you need to pass it through PYTHIA. Ask the developpers for the appropriate code.

Save the printout of PYTHIA in a .txt file.

The .txt file produced by PYTHIA needs to be stored in Ntuple. Use this code

pythia_root.C .

And you have the Ntuple, from the file generated by PYTHIA,ready for analysis.

MadGraph /MadEvent Installation, parton level analysis, PYTHIA


Download from http://madgraph.hep.uiuc.edu and unzip.

How to run step-by-step

Go to the Madgraph directory.

cp -r Template MyProcess
cd MyProcess

Edit the Cards/proc_card_mg5.dat , here you declare the process of interest and the decaying channels. If you specify the decaying products inside the proc_card_mg5.dat then the W and Z bosons are going to be generated on-shell if they do not be specified then W and Z bosons will also be produced offshell. You can of course avoid this obstacle by changing the cut off in the run_card.dat file.


Edit Cards/param_card.dat (here you declare parameters like BRs, coupling constants, etc..)

Edit Cards/run_card.dat (here you apply kinematical cuts, like ptjet>10...)

./bin/generate_events C1

C1 is just a string. So a folder named C1 has been created, containing weighted and unweighted events.

Store the MadGraph .lhe into Ntuples

So we want to store the info from the .lhe file, in order to do the analysis. Use this code

And you have the Ntuple, generated by MadGraph, ready for analysis.

You can continue inside Athena following the instructions here .

Or you can use the PYTHIA from helac mentiond before and follow the same procedure to get the Ntuple.

-- DespoinaSampsonidou - 2014-11-17

Topic attachments
I Attachment History Action Size Date Who Comment
C source code filec helac_to_ntuples.C r2 r1 manage 1.6 K 2014-11-27 - 11:41 DespoinaSampsonidou  
C source code filec pythia_root.C r2 r1 manage 3.2 K 2014-11-27 - 11:57 DespoinaSampsonidou  
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Topic revision: r5 - 2014-11-27 - DespoinaSampsonidou
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