2. Download the package which is "GeneratorInterface/Pythia8Interface".

- After get the authorized kerberos ticket -
cvs co -r CMSSW_2_2_3 GeneratorInterface/Pythia8Interface

3. Compile the Pythia8Interface?

scramv1 b

4. Edit the doc/pythia8_107 file. ( See the below )

<doc type="BuildSystem::ToolDoc" version="1.0"/>
<Tool name="pythia8_107" version="1.0">

<Environment name="LIBDIR" default="/opt/osg-app/cmssoft/cms/slc4_ia32_gcc345/external/pythia8/107-cms2/lib">
</Environment>

<Environment name="INCLUDE" default="/opt/osg-app/cmssoft/cms/slc4_ia32_gcc345/external/pythia8/107-cms2/include">
</Environment>

<lib name="pythia8"/>
<lib name="hepmcinterface"/>

<Runtime name="PYTHIA8DATA" value="/opt/osg-app/cmssoft/cms/slc4_ia32_gcc345/external/pythia8/107-cms2/xmldoc"/>
</Tool>

5. Setup the Pythia8Source? on scram

scramv1 setup pythia8_107 1.0 file:./pythia8_107

6. Copy the cfg file of Pythia6 to python/ directory.

7. Edit the cfg file.

#Input source
process.source = cms.Source("Pythia8Source",             // Change from PythiaSource to Pythia8Source. It is a very important.
    pythiaHepMCVerbosity = cms.untracked.bool(False),
    maxEventsToPrint = cms.untracked.int32(0),
    pythiaPylistVerbosity = cms.untracked.int32(0),
    comEnergy = cms.untracked.double(14000.0),
    PythiaParameters = cms.PSet(
        pythia8target = cms.vstring(                            // If you want, you can change the PSet name.
            'HardQCD:all = on',
            'PhaseSpace:pTHatMin = 20.'),
        parameterSets = cms.vstring('pythia8target')     // If you modify the PSet name, you should modify this, too.
    )

# Output definition
process.output = cms.OutputModule("PoolOutputModule",
    outputCommands = process.FEVTSIMEventContent.outputCommands,            // If you want a FEVTSIMEventContent(eg, GenParticle), you should change this.
    fileName = cms.untracked.string('pythia8_HardQCDpTcut20plusMinBias.root'),
    dataset = cms.untracked.PSet(
        dataTier = cms.untracked.string(''),
        filterName = cms.untracked.string('')
    ),
    SelectEvents = cms.untracked.PSet(
        SelectEvents = cms.vstring('generation_step')
    )
)

)

-- GunmoRyu - 08 Apr 2009