Difference: PythiattH (8 vs. 9)

Revision 92011-02-17 - GavinKirby

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META TOPICPARENT name="PythiattH"
-- GavinKirby - 2010-09-29
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This page documents the use of Pythia to generate ttH (Higgs-strahlung from top/tbar) events.
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This page documents the use of Pythia to generate ttH (Higgs-strahlung from top/tbar) events. The relevant code can be found in the Glasgow ATLAS subversion repository under Pythiatth. Note that in order to run it you will need to have the correct Pythia version in a directory called pythia6222, at the same level as the tth directory (this requirement is due to the linktth.sh script, which specifies the path to the Pythia version to use). This can be found in ~gkirby/Pythia_versions/pythia6222.
 
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  • src/tth.f -- the main Fortran source code,
  • inc/tth.inc -- contains variable declarations
  • inc/tth_inl.inc -- containing inline functions
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  • pycomm.inc --
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  • inc/pycomm.inc -- inline functions for Pythia variables
 
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The shell script test/linktth is used to compile the code.
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The shell script test/linktth.sh is used to compile the code. It creates two executable files: tth and tthsf (i.e. using structure functions).
  A run may be initiated in the test area by using the command

./tthsf < [filename].params > [output logfile]

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for a given parameters file. The code is set up to dump unsatisfactory events in the output logfile for debugging purposes.
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for a given parameters file. The code is set up to dump unsatisfactory events in the output (logfile) for debugging purposes.
 

Params Files

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tth.f

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This contains the main function (program higgs) and the subroutines it calls. The main function generates the required number of events (as specified by the .params file) and tests them to ensure that they comply with specific criteria (for debugging/sanity checking purposes). It also creates an output text file containing specific information about the generated events (the Boolean variable writeout is used to control which events are considered acceptable for this output file). The format of this output file is such that it can be parsed to create an ntuple using the relevant tools.
 

tth.inc

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This file contains variable declarations for the main program and each of the subroutines in tth.f: error counters, event particle counters and particle indices, as well as logical (Boolean) variables used in the main Fortran code.
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This file contains variable declarations for the main program and each of the subroutines in tth.f: error counters, event particle counters and particle indices, as well as logical (Boolean) variables used in the main Fortran code.
 

tth_inl.inc

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pycomm_inl.inc

This file contains inline functions relating to Pythia internal variables (e.g. the energy and momenta of particles). It assigns these values to a set of variables (declared in the file) which can then be used in the main function (e.g. for writeout of a text file containing event information suitable for building an ntuple).

 

Changes from VBF

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Particle Number Checking

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The code uses a number of independent checks to ensure that the events that Pythia is generating have the appropriate structure. In particular, it is important to check that the numbers of particles of each kind in an event are correct. For semileptonic ttH we expect to find one top, one tbar, one each of Wplus and Wminus (or two, for H->bbar), one lepton and its associated neutrino (or three leptons, for H->leptons), one (or two) each of b and bbar.
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The code uses a number of independent checks to ensure that the events that Pythia is generating have the anticipated structure. In particular, it is important to check that the numbers of particles of each kind in an event are correct. For semileptonic ttH we expect to find one top, one tbar, one each of Wplus and Wminus (or two, for H->bbar), one lepton and its associated neutrino (or three leptons, for H->leptons), one (or two) each of b and bbar. The code has been developed to focus specifically on H-->b/bbar, but can be modified for studies involving other Higgs decay modes.
 

Particle Parentage Checking

 
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