Class that helps perform 2-pronged boosted tagging using a reclustering in the jet's rest frame, supplemented with a cut on N-subjettiness (and a decay angle), as discussed by Ji-Hun Kim in arXiv:1011.1493. More...

#include <fastjet/tools/RestFrameNSubjettinessTagger.hh>

Inheritance diagram for fastjet::RestFrameNSubjettinessTagger:

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Collaboration diagram for fastjet::RestFrameNSubjettinessTagger:

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Public Types
typedef RestFrameNSubjettinessTaggerStructure	StructureType
	the type of Structure returned

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
	RestFrameNSubjettinessTagger (const JetDefinition subjet_def, const double tau2cut=0.08, const double costhetascut=0.8, const bool use_exclusive=false)
	ctor with arguments (see the class description above)

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
JetDefinition	_subjet_def

double	_t2cut

double	_costscut

bool	_use_exclusive

Detailed Description

Class that helps perform 2-pronged boosted tagging using a reclustering in the jet's rest frame, supplemented with a cut on N-subjettiness (and a decay angle), as discussed by Ji-Hun Kim in arXiv:1011.1493.

To tag a fat jet, the tagger proceeds as follows:

boost its constituents into the rest frame of the jet
recluster them using another jet definition (the original choice was SISCone in spherical coordinates with R=0.6 and f=0.75.
keep the 2 most energetic subjets ( $q_{1,2}$ ) and compute the 2-subjettiness
$\tau_2^j = \frac{2}{m_{\rm jet}^2}\, \sum_{k\in {\rm jet}} {\rm min}(q_1.p_k,q_2.p_k)$
where the sum runs over the constituents of the jet.
require $\tau_2^j < \tau_2^{\rm cut}$ [0.08 by default]
impose that (in the rest frame of the fat jet), the angles between the 2 most energetic subjets and the boost axis are both large enough: $\cos(\theta_s)<c_\theta^{\rm cut}$ [0.8 by default]

Note that in the original version, the jets to be tagged were reconstructed using SISCone with R=0.8 and f=0.75. Also, b-tagging was imposed on the 2 subjets found in the rest-frame tagging procedure.

Options

The constructor has the following arguments:

The first argument is the jet definition to be used to recluster the constituents of the jet to be filtered (in the rest frame of the tagged jet).
The second argument is the cut on tau_2 [0.08 by default]
The 3rd argument is the cut on cos(theta_s) [0.8 by default]
If the 4th argument is true, 2 exclusive rest-frame jets will be considered in place of the 2 most energetic inclusive jets

Input conditions

the original jet must have constituents

Output/structure

the 2 subjets are kept as pieces if some substructure is found, otherwise a single 0-momentum piece
the tau2 and maximal cos(theta_s) values computed during the tagging can be obtained via the resulting jet's structure_of<...>() function

Definition at line 101 of file RestFrameNSubjettinessTagger.hh.