TWINPHOX version 1.0

Structure of the program

Installation

1. Load the TWINPHOX code as gzipped .tar file and unpack it.
2. In the directory "working", there is a Makefile (using the GNU makefile).
   
   1. The user has to verify that the fortran compiler called in the Makefile is the one implemented on his machine.
      The default is the f77 DEC fortran compiler FC = f77. On Linux PCs use the GNU compiler g77.
   2. Options of compilation:
      FFLAGS = -O : the compilation flag FFLAGS = -O corresponds to the default level of optimization used by the f77 DEC
      compiler (it works also with g77). For any alternative choice of optimization, please see your compiler's manual.
   3. The user has to verify that the choice of the makefile to build the BASES library is the one corresponding to his machine.
      One can choose between:
      Makefile.dec, Makefile.f2c, Makefile.hiux, Makefile.hpux, Makefile.sgi, Makefile.sun, Makefile.tpl, Makefile.linux
      depending on the computer to be used. The default is
      MAKEBASES = Makefile.dec
   4. The program uses the exe cernlib which is not provided with the program package because it is very likely that the cernlib
      is already installed on your system (if not you can get it from the CERN program library ).
      The user has to verify that the path to the CERN library on his system has been set correctly.
      Default: PATHCERNLIB = cern/pro/bin


3. Run once the Makefile with the option bases ("gmake bases") to create the library for Bases/Spring.

To run the program

1. Fix the input parameters of your choice in the file "parameter.indat" in the directory "working".
   This is the main input file containing the parameters for integration and event generation.
   Further information on these parameters is given directly in this file.
   If you also would like to project events into histograms, define the corresponding parameters in the file "param_histo.indat".
2. To run the perl script "start.pl" which creates the executable files, type "perl start.pl". This does the following:
   1. The two files "parameter.indat" and "param_histo.indat" containing the input parameters are read automatically.
      In case you have several parameter files with different names, you simply have to specify the names of your parameter files as options: type
      "perl start.pl --parameter your_parameterfilename --histo your_param_histofilename".
      Note that "param_histo.indat" will be read only if the flag "histo" in the file "parameter.indat" has been selected.
      
   2. start.pl automatically rewrites the Makefile according to the options you chose in "parameter.indat", and runs the compiler.
   3. start.pl creates an executable file called "run_string.exe" where "string" is the name of the run defined in "parameter.indat". You have to execute this file with your favorite options.
   4. start.pl creates a directory called "resultstring".
      In this directory, there will be a file "histoNameHisto.outdat" containing a summary of the input which "start.pl" has read from "param_histo.indat". The string NameHisto used to label the files containing the histograms (or the ntuple) is defined in "parameter.indat".
      The directory "resultstring" also will contain subdirectories called
      "dddstring" and/or
      "drdstring"
      "rddstring"
      "rrdstring"
      depending on which subprocesses you selected in your input. The shorthand "ddd" stands for the contribution where both the initial state and the final state photons are direct. (Note that the final state photon is always direct when using Frixione's isolation criterium, since the fragmentation part does not contribute.) In "drd" the initial state photon travelling in positive z-direction is direct and the other one is resolved, in "rdd" the reverse is true. In "rrd" both photons are resolved. So the structure of the output is the following:
      
      

      resultstring
      histoNameHisto.outdat	dddstring	drdstring	rddstring	rrdstring
      parameters read from "param_histo.indat"	output files specified below	see below	see below	see below

      "output.param"	parameters read from parameter.indat
      "sigmaint.res"	physical integrated cross-section
      "integral.res"	results of integration of absolute values of pseudo-cross sections; no physical meaning, needed for normalization of generated events
      "*.bs"	results of the grid for each pseudo-cross section; needed for event generation
      "twinphox.log"	details of the integration by BASES (efficiency, convergence behaviour, accuracy,time per point, ...)

Comments

• With twinphox, we provide the AFG and the new AFG02 parton distribution functions for the real photon, but the user can choose other pdfs from the CERN pdflib (see parameter.indat).



• In the input file "parameter.indat" you have to choose between two options:
  
  • either to compute the integrated cross section over the phase space defined by the cuts
  
  
  • or to make the grid and generate events.
  If you you are not interested in integrated cross sections, set the corresponding flag to "FALSE" and make directly the grids in order to save integration time. You do not need to calculate first the integrated cross section in order to make the grid and/or generate events.



• If you want to generate isolated photon events, you have to apply the isolation cuts already when making the grids.



• Once you have produced the grids (stored in the *.bs files), you can use them again to generate new events and enlarge an existing event sample without having to recompute grids. However if you are interested in a kinematic range which is not populated efficiently by the existing grids, keeping these grids will generate too many events that further will be lost in the histrogramming stage. In such a case the computation of a new dedicated grid is much more efficient in the end.



• If you chose the option "histo" in your input to produce directly histograms instead of passing via ntuples, you can refine some cuts already defined in "parameter.indat" and specify the histograms you want in the file "param_histo.indat" (there is a list of defined cut-parameters and variables in "param_histo.indat"). When running "start.pl" the corresponding Fortran files to fill the histograms with the specified cuts are created automatically.



• You can use the information given in the file "twinphox.log" to adjust the parameters for BASES/SPRING such that the efficiency is optimized.



• Please contact gudrun@physik.unizh.ch in case you have any questions or comments.

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