MarlinFastJet Documentation

Description

MarlinFastJet is a small wrapper around the FastJet library for Jet Finding.
It has access to a many of the Infrared and Collinear Safe jet finding algorithms like kt_algorithm, anti_kt_algorithm and SISCone.

Available Algorithms

The most used algorithms are kt_algorithm, cambridge_algorithm, antikt_algorithm, ee_kt_algorithm and SISConePlugin. For a complete list start the processor and look at the log (MESSAGE). The corresponding parameter is "algorithm", and it takes at least the algorithm name, plus its paramers (if any, typically R).

Clustering Modes

This processor support 4 different kind of clustering modes, but not each mode is supported by each algorithm. It can be set via the parameter "clusteringMode" in the steering file.

We have available:

• Inclusive <minPt>: Clusters the entire event.
• InclusiveIterativeNJets <NJets> <minE>: Clusters the entire event, but tries to modify the R parameter of the used algorithm to get exactly <NJets> with a minimum energy of <minE>. Very CPU intensive and might not be Infrared Safe.
• ExclusiveNJets <NJets>: Clusters event until exactly <Njets> are found, but introduces "beam jets" close to the beam axis. These "beam jets" are meant for the remnants of the proton at a hadron collider, and get rejected. Saves the value of YCut at which N-1 (N+1) jets would have been found in the LCEvent.
• ExclusiveYCut <YCut>: As ExclusiveNJets, but stops when the minimal distance of 2 jets is at <YCut>

Example steering file

<marlin xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://ilcsoft.desy.de/marlin/marlin.xsd">
<execute>
<processor name="MyFastJetProcessor">
<processor name="MyLCIOOutputProcessor">
</execute>

<global>
<parameter name="LCIOInputFiles"> myfile.slcio </parameter>
<parameter name="SkipNEvents" value="0">
<parameter name="SupressCheck" value="false">
<parameter name="Verbosity" options="DEBUG0-4,MESSAGE0-4,WARNING0-4,ERROR0-4,SILENT"> MESSAGE </parameter>
</global>

    <processor name="MyFastJetProcessor" type="FastJetProcessor"> <br />
            <parameter name="algorithm" type="StringVec">kt_algorithm 0.75</parameter> <br />
            <parameter name="clusteringMode" type="StringVec"> InclusiveIterativeNJets 4 10</parameter> <br />
            <parameter name="jetOut" type="string" lcioOutType="ReconstructedParticle">JetOut </parameter> <br />
            <parameter name="recParticleIn" type="string" lcioInType="ReconstructedParticle"> PandoraPFANewPFOs </parameter> <br />
            <parameter name="recombinationScheme" type="string">E_scheme </parameter> <br />
    </processor> <br />

    <processor name="MyLCIOOutputProcessor" type="LCIOOutputProcessor"> <br />
            <parameter name="LCIOOutputFile" type="string">outputfile.slcio </parameter> <br />
            <parameter name="LCIOWriteMode" type="string">WRITE_NEW</parameter> <br />
            <br />
    </processor> <br />

</marlin>