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:

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Collaboration diagram for fastjet::MassDropTagger:

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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()).
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.

Protected Attributes
double	_mu
double	_ycut

Static Protected Attributes
static LimitedWarning	_warnings_nonca
static LimitedWarning	_negative_mass_warning

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:

start from a jet obtained from with the Cambridge/Aachen algorithm
undo the last step of the clustering step j -> j1 + j2 (label them such as j1 is the most massive).
if there is a mass drop, i.e. m_j1/m_j < mu_cut, and the splitting is sufficiently symmetric, ${\rm min}(p_{tj1}^2,p_{tj2}^2)\Delta R_{j1,j2}^2 > y_{\rm cut} m_j^2$ , keep j as the result of the tagger (with j1 and j2 its 2 subjets)
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 Typedef Documentation

◆ StructureType

typedef MassDropTaggerStructure fastjet::MassDropTagger::StructureType

the type of the associated structure

Definition at line 107 of file MassDropTagger.hh.

Constructor & Destructor Documentation

◆ MassDropTagger()

fastjet::MassDropTagger::MassDropTagger	(	const double	mu = 0.67,
		const double	ycut = 0.09 )

inline

default ctor

Definition at line 95 of file MassDropTagger.hh.

Member Function Documentation

◆ description()

string fastjet::MassDropTagger::description ( ) const

virtual

returns a textual description of the tagger

Implements fastjet::Transformer.

Definition at line 48 of file MassDropTagger.cc.

◆ result()

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 57 of file MassDropTagger.cc.

Member Data Documentation

◆ _mu

double fastjet::MassDropTagger::_mu

protected

Definition at line 110 of file MassDropTagger.hh.

◆ _ycut

double fastjet::MassDropTagger::_ycut

protected

Definition at line 110 of file MassDropTagger.hh.

◆ _warnings_nonca

LimitedWarning fastjet::MassDropTagger::_warnings_nonca

staticprotected

Definition at line 111 of file MassDropTagger.hh.

◆ _negative_mass_warning

LimitedWarning fastjet::MassDropTagger::_negative_mass_warning