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README file for running the GoSam+Sherpa process packages:
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These packages allow to compute NLO corrections in QCD.

Executing the script 'makecode' will unpack and compile the virtual code 
generated with GoSam and generate the libraries for the born, real and 
subtraction terms. Just execute 

./makecode install

During the compilation time the code for the virtual part is compiled
and the libraries for the tree-level diagrams are generated by AMEGIC. 
During this stage AMEGIC writes some WARNING statements, which are normal
and can safely be ignored.
Once the compilation is completed everything is ready to perform
analysis. The package provides two possibilities:

- use GoSam+Sherpa with the internal analysis package of Sherpa

  --> the card 'Run_LO.dat' allows to compute the
      process al leading order,

  --> the card 'Run_NLO.dat' allows to compute the
      process al next-to-leading order and contains
      all contributions (Born/Real/Subtrac/Virtual),

- use GoSam+Sherpa in association with Rivet for the analysis

  --> for this the Sherpa input card Run_Rivet.dat
      can be used for the full NLO analysis.
      
      WARNING: Rivet at the moment gives wrong statistical
      		errors for NLO calculations!!

All the created files can be removed at any time with

./makecode clean


After full compilation of the code, the cards can be run using either 
of the commands:

Sherpa -f Run_LO.dat
Sherpa -f Run_NLO.dat
Sherpa -f Run_Rivet.dat

The provided 'makeplots' script allows to produce plots from the .dat files
with the distributions which are created in the 'Analysis' directory.
By default the script reads the files from the 'Analysis' directory and
produces a gnuplot file 'SherpaPlots.gnu'and a file with plots called
'GoSam+Sherpa_Plots.ps' both in the 'Plots' folder.
You can alternatively specify input directory, output directory and output
file name with the options '-i' (--input=), '-d' (--outdir) and '-o'
(--output) respectively.
For more details about the usage of the 'makeplots' script try

./makeplots -h   or   ./makeplots --help


Brief description of the files:
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When unpacking the tarball a directory with the name of the process is crated, 
with the following files:

-gosam_process_process_name-1.0.tar.gz : tarball of the virtual code

-makecode: script to generate/clean the process
-makeplots: script to produce plots from .dat file using gnuplot

-OLE_order.lh : BLHA interface order file
-OLE_order.olc: BLHA interface contract file
	      --> these two files are used for the comunication
	      	  between Sherpa and GoSam. They are needed for
		  Sherpa to call the correct virtual partonic 
		  subprocess.

-Run_LO.dat : Sherpa card for Born
-Run_NLO.dat: Sherpa card for NLO with Born/Real/Sub.terms/Virtual/Int.sub.terms

-Run_Rivet.dat: Sherpa card to be used with Rivet.

-References.tex: List of References used to by the generated code

-README: this README file

  * * * 

Once the code is generated in the directory there are the following further files:

Analysis: directory where the Sherpa/Rivet analysis files are written
Process : directory with Sherpa libraries of the matrix elements of the process
Virtul_processname: directory with GoSam code for the virtual part


References:
GoSam   -- http://gosam.hepforge.org
Sherpa  -- http://sherpa.hepforge.org