fastjet::Pruner Class Reference

Transformer that prunes a jet. More...

#include <fastjet/tools/Pruner.hh>

Inheritance diagram for fastjet::Pruner:

Collaboration diagram for fastjet::Pruner:

List of all members.

Public Types
typedef PrunerStructure	StructureType
	A typedef that is needed to ensure that the PseudoJet::structure_of() template function works.
Public Member Functions
	Pruner (const JetAlgorithm jet_alg, double zcut, double Rcut_factor)
	minimal constructor, which takes a jet algorithm, sets the radius to JetDefinition::max_allowable_R (practically equivalent to infinity) and also tries to use a recombiner based on the one in the jet definition of the particular jet being pruned.
	Pruner (const JetDefinition &jet_def, double zcut, double Rcut_factor)
	alternative ctor in which the full reclustering jet definition can be specified.
	Pruner (const JetDefinition &jet_def, FunctionOfPseudoJet< double > *zcut_dyn, FunctionOfPseudoJet< double > *Rcut_dyn)
	alternative ctor in which the pt-fraction cut and angular distance cut are functions of the jet being pruned.
virtual PseudoJet	result (const PseudoJet &jet) const
	action on a single jet
virtual std::string	description () const
	description

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Detailed Description

Transformer that prunes a jet.

This transformer prunes a jet according to the ideas presented in arXiv:0903.5081 (S.D. Ellis, C.K. Vermilion and J.R. Walsh).

The jet's constituents are reclustered with a user-specified jet definition, with the modification that objects i and j are only recombined if at least one of the following two criteria is satisfied:

• the geometric distance between i and j is smaller than 'Rcut' with Rcut = Rcut_factor*2m/pt (Rcut_factor is a parameter of the Pruner and m and pt obtained from the jet being pruned)
• the transverse momenta of i and j are at least 'zcut' p_t(i+j)

If both these criteria fail, i and j are not recombined, the harder of i and j is kept, and the softer is rejected.

Usage:

    Pruner pruner(jet_def, zcut, Rcut_factor);
    PseudoJet pruned_jet = pruner(jet);

The pruned_jet has a valid associated cluster sequence. In addition the subjets of the original jet that have been vetoed by pruning (i.e. have been 'pruned away') can be accessed using

   vector<PseudoJet> rejected_subjets = pruned_jet.structure_of<Pruner>().rejected();

If the re-clustering happens to find more than a single inclusive jet (this should normally not happen if the radius of the jet definition used for the reclustering was set large enough), the hardest of these jets is retured as the result of the Pruner. The other jets can be accessed through

   vector<PseudoJet> extra_jets = pruned_jet.structure_of<Pruner>().extra_jets();

Instead of using Rcut_factor and zcut, one can alternatively construct a Pruner by passing two (pointers to) functions of PseudoJet that dynamically compute the Rcut and zcut to be used for the jet being pruned.

When the jet being pruned has area support and explicit ghosts, the resulting pruned jet will likewise have area.

Definition at line 100 of file Pruner.hh.

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Constructor & Destructor Documentation

fastjet::Pruner::Pruner	(	const JetAlgorithm	jet_alg,
		double	zcut,
		double	Rcut_factor
	)		[inline]

minimal constructor, which takes a jet algorithm, sets the radius to JetDefinition::max_allowable_R (practically equivalent to infinity) and also tries to use a recombiner based on the one in the jet definition of the particular jet being pruned.

Parameters:

jet_alg	the jet algorithm for the internal clustering
zcut	pt-fraction cut in the pruning
Rcut_factor	the angular distance cut in the pruning will be Rcut_factor * 2m/pt

Definition at line 111 of file Pruner.hh.

fastjet::Pruner::Pruner	(	const JetDefinition &	jet_def,
		double	zcut,
		double	Rcut_factor
	)		[inline]

alternative ctor in which the full reclustering jet definition can be specified.

Parameters:

jet_def	the jet definition for the internal clustering
zcut	pt-fraction cut in the pruning
Rcut_factor	the angular distance cut in the pruning will be Rcut_factor * 2m/pt

Definition at line 124 of file Pruner.hh.

fastjet::Pruner::Pruner	(	const JetDefinition &	jet_def,
		FunctionOfPseudoJet< double > *	zcut_dyn,
		FunctionOfPseudoJet< double > *	Rcut_dyn
	)

alternative ctor in which the pt-fraction cut and angular distance cut are functions of the jet being pruned.

Parameters:

jet_def	the jet definition for the internal clustering
zcut_dyn	dynamic pt-fraction cut in the pruning
Rcut_dyn	dynamic angular distance cut in the pruning

Definition at line 52 of file Pruner.cc.

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The documentation for this class was generated from the following files:

• tools/fastjet/tools/Pruner.hh
• tools/Filter.cc
• tools/Pruner.cc