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ClusterSequence_N2.cc
//FJSTARTHEADER
// $Id$
//
// Copyright (c) 2005-2021, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
//
//----------------------------------------------------------------------
// This file is part of FastJet.
//
// FastJet is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// The algorithms that underlie FastJet have required considerable
// development. They are described in the original FastJet paper,
// hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
// FastJet as part of work towards a scientific publication, please
// quote the version you use and include a citation to the manual and
// optionally also to hep-ph/0512210.
//
// FastJet is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with FastJet. If not, see <http://www.gnu.org/licenses/>.
//----------------------------------------------------------------------
//FJENDHEADER
// The plain N^2 part of the ClusterSequence class -- separated out
// from the rest of the class implementation so as to speed up
// compilation of this particular part while it is under test.
#include "fastjet/internal/ClusterSequence_N2.icc"
#include<iostream>
FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
using namespace std;
//*************************************************************************
//
// THINGS FOR E+E-
//
//*************************************************************************
//----------------------------------------------------------------------
template<> inline void ClusterSequence::_bj_set_jetinfo(
EEBriefJet * const jetA, const int _jets_index) const {
double E = _jets[_jets_index].E();
double scale = E*E; // the default energy scale for the kt alg
double p = jet_def().extra_param(); // in case we're ee_genkt
switch (_jet_algorithm) {
case ee_kt_algorithm:
assert(_Rparam > 2.0); // force this to be true! [not best place, but works]
// recall that _invR2 is artificially set to 1 for this alg
// so that we automatically have dij = scale * 2(1-cos theta_ij)
// Normally, _Rparam should be automatically set to 4 from JetDefinition
break;
case ee_genkt_algorithm:
if (p <= 0 && scale < 1e-300) scale = 1e-300; // same dodgy safety as genkt
scale = pow(scale,p);
break;
default:
throw Error("Unrecognised jet algorithm");
}
jetA->kt2 = scale; // "kt2" might one day be renamed as "scale" or some such
double norm = _jets[_jets_index].modp2();
if (norm > 0) {
norm = 1.0/sqrt(norm);
jetA->nx = norm * _jets[_jets_index].px();
jetA->ny = norm * _jets[_jets_index].py();
jetA->nz = norm * _jets[_jets_index].pz();
} else {
jetA->nx = 0.0;
jetA->ny = 0.0;
jetA->nz = 1.0;
}
jetA->_jets_index = _jets_index;
// initialise NN info as well
jetA->NN_dist = _R2;
jetA->NN = NULL;
}
//----------------------------------------------------------------------
// returns the angular distance between the two jets
template<> double ClusterSequence::_bj_dist(
const EEBriefJet * const jeta,
const EEBriefJet * const jetb) const {
double dist = 1.0
- jeta->nx*jetb->nx
- jeta->ny*jetb->ny
- jeta->nz*jetb->nz;
dist *= 2; // distance is _2_*min(Ei^2,Ej^2)*(1-cos theta)
return dist;
}
// get explicit copies of the two N2 cluster cases we need
// plain BriefJet
void ClusterSequence::_simple_N2_cluster_BriefJet() {
_simple_N2_cluster<BriefJet>();
}
// e+e- BriefJet
void ClusterSequence::_simple_N2_cluster_EEBriefJet() {
_simple_N2_cluster<EEBriefJet>();
}
// //----------------------------------------------------------------------
// /// Force instantiation of desired versions of _simple_N2_cluster
// ///
// /// This is not very elegant...
// void ClusterSequence::_dummy_N2_cluster_instantiation() {
// _simple_N2_cluster<BriefJet>();
// _simple_N2_cluster<EEBriefJet>();
// }
FASTJET_END_NAMESPACE
fastjet::norm
double norm(const VPoint p)
norm of a vector
Definition Voronoi.hh:155
fastjet::ee_genkt_algorithm
@ ee_genkt_algorithm
the e+e- genkt algorithm (R > 2 and p=1 gives ee_kt)
Definition JetDefinition.hh:165
fastjet::ee_kt_algorithm
@ ee_kt_algorithm
the e+e- kt algorithm
Definition JetDefinition.hh:163