fastjet::MassDropTagger Class Reference

Class that helps perform 2-pronged boosted tagging using the "mass-drop" technique (with asymmetry cut) introduced by Jonathan Butterworth, Adam Davison, Mathieu Rubin and Gavin Salam in arXiv:0802.2470 in the context of a boosted Higgs search. More...

#include <fastjet/tools/MassDropTagger.hh>

Inheritance diagram for fastjet::MassDropTagger:

Collaboration diagram for fastjet::MassDropTagger:

Public Types
typedef MassDropTaggerStructure	StructureType
	the type of the associated structure
Public Types inherited from fastjet::Transformer
typedef PseudoJetStructureBase	StructureType
	A typedef that is needed to ensure that the PseudoJet::structure_of() template function works.

Public Member Functions
	MassDropTagger (const double mu=0.67, const double ycut=0.09)
	default ctor
virtual std::string	description () const
	returns a textual description of the tagger
virtual PseudoJet	result (const PseudoJet &jet) const
	runs the tagger on the given jet and returns the tagged PseudoJet if successful, a PseudoJet==0 otherwise (standard access is through operator()). More...
Public Member Functions inherited from fastjet::Transformer
	Transformer ()
	default ctor
virtual	~Transformer ()
	default dtor
Public Member Functions inherited from fastjet::FunctionOfPseudoJet< PseudoJet >
	FunctionOfPseudoJet ()
	default ctor
virtual	~FunctionOfPseudoJet ()
	default dtor (virtual to allow safe polymorphism)
PseudoJet	operator() (const PseudoJet &pj) const
	apply the function using the "traditional" () operator. More...
std::vector< PseudoJet >	operator() (const std::vector< PseudoJet > &pjs) const
	apply the function on a vector of PseudoJet, returning a vector of the results. More...

Protected Attributes
double	_mu
double	_ycut

Static Protected Attributes
static LimitedWarning	_warnings_nonca

Detailed Description

Class that helps perform 2-pronged boosted tagging using the "mass-drop" technique (with asymmetry cut) introduced by Jonathan Butterworth, Adam Davison, Mathieu Rubin and Gavin Salam in arXiv:0802.2470 in the context of a boosted Higgs search.

The tagger proceeds as follows:

0. start from a jet obtained from with the Cambridge/Aachen algorithm

1. undo the last step of the clustering step j -> j1 + j2 (label them such as j1 is the most massive).
2. if there is a mass drop, i.e. m_j1/m_j < mu_cut, and the splitting is sufficiently symmetric, , keep j as the result of the tagger (with j1 and j2 its 2 subjets)
3. otherwise, redefine j to be equal to j1 and return to step 1.

Note that in the original proposal, j1 and j2 are both required to be b-tagged and a filter (with Rfilt=min(0.3,Rbb/2) and n_filt=3) is also applied to j to obtain the final "Higgs candidate". See the example 12 - boosted Higgs tagging for details.

Options

The constructor has the following arguments:

• The first argument is the minimal mass drop that is required (mu_cut) [0.67 by default]
• The second argument is the asymmetry cut (y_cut) [0.09 by default]

Input conditions

• one must be able to successively "uncluster" the original jet using "has_parents"

Output/structure

• the 2 subjets are kept as pieces if some substructure is found, otherwise a single 0-momentum piece is returned
• the 'mu' and 'y' values corresponding to the unclustering step that passed the tagger's cuts

See also 12 - boosted Higgs tagging for a usage example.

Definition at line 92 of file MassDropTagger.hh.

Member Function Documentation

PseudoJet fastjet::MassDropTagger::result ( const PseudoJet &  jet ) const

virtual

runs the tagger on the given jet and returns the tagged PseudoJet if successful, a PseudoJet==0 otherwise (standard access is through operator()).

Parameters

jet	the PseudoJet to tag

Implements fastjet::Transformer.

Definition at line 56 of file MassDropTagger.cc.

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

• tools/fastjet/tools/MassDropTagger.hh
• tools/MassDropTagger.cc