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// Njettiness Package
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// Version 0.4.1 (January 22, 2012)
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// Questions/Comments? jthaler@jthaler.net
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// Copyright (c) 2011-12, Jesse Thaler, Ken Van Tilburg, and Christopher K.
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// Vermilion
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//
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//----------------------------------------------------------------------
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// This file is part of the N-jettiness package ("N-jettiness").
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//
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// N-jettiness is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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//
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// SpartyJet is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with SpartyJet; if not, write to the Free Software
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// Foundation, Inc.:
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// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//----------------------------------------------------------------------
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#ifndef __NJETTINESSPLUGIN_HH__
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#define __NJETTINESSPLUGIN_HH__
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#include "Njettiness.hh"
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#include "fastjet/ClusterSequence.hh"
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#include "fastjet/JetDefinition.hh"
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#include <string>
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#include <climits>
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FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
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/// The Njettiness jet algorithm
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/**
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* An exclusive jet finder that identifies N jets; first N axes are found, then
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* particles are assigned to the nearest (DeltaR) axis and for each axis the
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* corresponding jet is simply the four-momentum sum of these particles.
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*
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* Axes can be found in several ways, specified by the AxesMode argument:
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*
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* kt_axes : exclusive kT
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* ca_axes : exclusive CA
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* min_axes : minimize N-jettiness by iteration (100 passes default)
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* onepass_{kt,ca}_axes : one-pass minimization seeded by kt or CA (pretty good)
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*
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* N-jettiness is defined as:
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*
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* tau_N = Sum_{all particles i}
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* p_T^i min((DR_i1/R_0)^beta, (DR_i2/R_0)^beta, ... , 1)
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*
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* DR_ij is the distance sqrt(Delta_phi^2 + Delta_rap^2) between particle i
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* and jet j. R_0 and beta are parameters of the algorithm. R_0 effectively
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* defines an angular cutoff similar in effect to a cone-jet radius.
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*
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* You can also specify an angular cutoff Rcutoff. Particles within R0 of an
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* axis affect tau_N, but only particles with Rcutoff are included in the final
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* jets. In principal Rcutoff can be smaller of larger than R0. Rcutoff=inf
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* corresponds to a partition of the event such that all particles are assigned
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* to jets.
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*
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*/
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class NjettinessPlugin : public JetDefinition::Plugin {
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public:
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NjettinessPlugin(int N, Njettiness::AxesMode mode, double beta, double R0, double Rcutoff=std::numeric_limits<double>::max());
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// The things that are required by base class.
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virtual std::string description () const;
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virtual double R() const {return -1.0;} // todo: make this not stupid
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virtual void run_clustering(ClusterSequence&) const;
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virtual ~NjettinessPlugin() {}
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private:
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int _N;
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mutable Njettiness _njettinessFinder; // should muck with this so run_clustering can be const without this mutable
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};
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inline NjettinessPlugin::NjettinessPlugin(int N, Njettiness::AxesMode mode, double beta, double R0, double Rcutoff)
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: _N(N), _njettinessFinder(mode, NsubParameters(beta, R0, Rcutoff))
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{}
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inline std::string NjettinessPlugin::description() const {return "NJettiness";}
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inline void NjettinessPlugin::run_clustering(ClusterSequence& cs) const
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{
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std::vector<fastjet::PseudoJet> particles = cs.jets();
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_njettinessFinder.getTau(_N, particles);
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std::vector<std::list<int> > partition = _njettinessFinder.getPartition(particles);
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// output clusterings for each jet
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for (size_t i = 0; i < partition.size(); ++i) {
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std::list<int>& indices = partition[i];
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if (indices.size() == 0) continue;
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std::list<int>::const_iterator it = indices.begin();
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while (indices.size() > 1) {
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int merge_i = indices.back(); indices.pop_back();
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int merge_j = indices.back(); indices.pop_back();
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int newIndex;
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double fakeDij = -1.0;
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cs.plugin_record_ij_recombination(merge_i, merge_j, fakeDij, newIndex);
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indices.push_back(newIndex);
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}
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double fakeDib = -1.0;
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cs.plugin_record_iB_recombination(indices.back(), fakeDib);
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}
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}
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FASTJET_END_NAMESPACE // defined in fastjet/internal/base.hh
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#endif // __NJETTINESSPLUGIN_HH__
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