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//----------------------------------------------------------------------
/// \file
/// \page Example06 06 - using jet areas
///
/// fastjet example program for jet areas
/// It mostly illustrates the usage of the
/// fastjet::AreaDefinition and fastjet::ClusterSequenceArea classes
///
/// run it with : ./06-area < data/single-event.dat
///
/// Source code: 06-area.cc
//----------------------------------------------------------------------
//STARTHEADER
// $Id: 06-area.cc 2684 2011-11-14 07:41:44Z soyez $
//
// Copyright (c) 2005-2011, 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 and are described in hep-ph/0512210. If you use
// FastJet as part of work towards a scientific publication, please
// include a citation to the FastJet paper.
//
// 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/>.
//----------------------------------------------------------------------
//ENDHEADER
#include "fastjet/ClusterSequenceArea.hh" // use this instead of the "usual" ClusterSequence to get area support
#include <iostream> // needed for io
#include <cstdio> // needed for io
using namespace std;
/// an example program showing how to use fastjet
int main(){
// read in input particles
//----------------------------------------------------------
vector<fastjet::PseudoJet> input_particles;
double px, py , pz, E;
while (cin >> px >> py >> pz >> E) {
// create a fastjet::PseudoJet with these components and put it onto
// back of the input_particles vector
input_particles.push_back(fastjet::PseudoJet(px,py,pz,E));
}
// create a jet definition:
// a jet algorithm with a given radius parameter
//----------------------------------------------------------
double R = 0.6;
fastjet::JetDefinition jet_def(fastjet::kt_algorithm, R);
// Now we also need an AreaDefinition to define the properties of the
// area we want
//
// This is made of 2 building blocks:
// - the area type:
// passive, active, active with explicit ghosts, or Voronoi area
// - the specifications:
// a VoronoiSpec or a GhostedAreaSpec for the 3 ghost-bases ones
//
//---------------------------------------------------------- For
// GhostedAreaSpec (as below), the minimal info you have to provide
// is up to what rapidity ghosts are placed.
// Other commonm parameters (that mostly have an impact on the
// precision on the area) include the number of repetitions
// (i.e. the number of different sets of ghosts that are used) and
// the ghost density (controlled through the ghost_area).
// Other, more exotic, parameters (not shown here) control how ghosts
// are placed.
//
// The ghost rapidity interval should be large enough to cover the
// jets for which you want to calculate. E.g. if you want to
// calculate the area of jets up to |y|=4, you need to put ghosts up
// to at least 4+R (or, optionally, up to the largest particle
// rapidity if this is smaller).
double maxrap = 5.0;
unsigned int n_repeat = 3; // default is 1
double ghost_area = 0.01; // this is the default
fastjet::GhostedAreaSpec area_spec(maxrap, n_repeat, ghost_area);
fastjet::AreaDefinition area_def(fastjet::active_area, area_spec);
// run the jet clustering with the above jet and area definitions
//
// The only change is the usage of a ClusterSequenceArea rather than
//a ClusterSequence
//----------------------------------------------------------
fastjet::ClusterSequenceArea clust_seq(input_particles, jet_def, area_def);
// get the resulting jets ordered in pt
//----------------------------------------------------------
double ptmin = 5.0;
vector<fastjet::PseudoJet> inclusive_jets = sorted_by_pt(clust_seq.inclusive_jets(ptmin));
// tell the user what was done
// - the description of the algorithm and area used
// - extract the inclusive jets with pt > 5 GeV
// show the output as
// {index, rap, phi, pt, number of constituents}
//----------------------------------------------------------
cout << endl;
cout << "Ran " << jet_def.description() << endl;
cout << "Area: " << area_def.description() << endl << endl;
// label the columns
printf("%5s %15s %15s %15s %15s %15s\n","jet #", "rapidity", "phi", "pt", "area", "area error");
// print out the details for each jet
for (unsigned int i = 0; i < inclusive_jets.size(); i++) {
printf("%5u %15.8f %15.8f %15.8f %15.8f %15.8f\n", i,
inclusive_jets[i].rap(), inclusive_jets[i].phi(), inclusive_jets[i].perp(),
inclusive_jets[i].area(), inclusive_jets[i].area_error());
}
return 0;
}
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