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CDFMidPointPlugin.hh
//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
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// (at your option) any later version.
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// hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
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#ifndef __CDFMIDPOINTPLUGIN_HH__
#define __CDFMIDPOINTPLUGIN_HH__
#include "fastjet/JetDefinition.hh"
#include "fastjet/internal/thread_safety_helpers.hh" // helpers to write transparent code w&wo C++11 features
// questionable whether this should be in fastjet namespace or not...
FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
//----------------------------------------------------------------------
//
/// @ingroup plugins
/// \class CDFMidPointPlugin
/// Implementation of the MidPoint algorithm from CDF (plugin for
/// fastjet-v2.1 upwards)
///
/// A plugin for fastjet-v2.1 that provides an interface to the CDF
/// midpoint algorithm
///
/// CDFMidPointPlugin is a plugin for fastjet (v2.1 upwards) that
/// provides an interface to the CDF version of Run-II iterative cone
/// algorithm with midpoint seeds (also known as the Iterative Legacy
/// Cone Algorithm, ILCA).
///
/// The CDF code has been taken from Joey Huston's webpage
/// http://www.pa.msu.edu/~huston/Les_Houches_2005/Les_Houches_SM.html
///
/// Note that the CDF midpoint code contains options that go beyond
/// those described in the Tevatron run-II document (hep-ex/0005012),
/// notably search-cones, as described in hep-ph/0111434, and
/// midpoints bewteen multiplets of stable cones.
///
/// Additionally, the version of the CDF midpoint code distributed
/// here has been modified by the FastJet authors, so as to allow one
/// to choose the scale used in the split-merge step.
//
//----------------------------------------------------------------------
class CDFMidPointPlugin : public JetDefinition::Plugin {
public:
/// the choice of scale to be used in the split-merge step
// NB: just replicates what we've added to the CDF midpoint code
enum SplitMergeScale {SM_pt, SM_Et, SM_mt, SM_pttilde};
///
/// A CDFMidPointPlugin constructor that looks like the one provided
/// by CDF. Its arguments should have the following meaning:
///
/// - seed_threshold: minimum pt for a particle to be considered
/// a seed of the iteration.
///
/// - cone_radius: standard meaning
///
/// - cone_area_fraction: stable-cones are searched for with a
/// radius Rsearch = R * sqrt(cone_area_fraction), and then
/// expanded to size R afterwards; note (hep-ph/0610012) that this
/// introduces IR unsafety at NLO for X+2-jet observables (where X
/// any hard object).
///
/// - max_pair_size: "midpoints" can be added between pairs of
/// stable cones, triplets of stable cones, etc.; max_pair_size
/// indicates the maximum number of stable cones that are
/// assembled when adding midpoints.
///
/// - max_iterations: the maximum number of iterations to carry out
/// when looking for a stable cone.
///
/// - overlap_threshold: if
/// (overlapping_Et)/(Et_of_softer_protojet) < overlap_threshold,
/// overlapping jets are split, otherwise they are merged.
///
/// - sm_scale: a choice for the scale to be used in the split-merge
/// step (both for ordering the momenta and quantifying the
/// overlap); the three options are
///
/// . SM_pt: pt (default -- source of small IR safety issue in purely
/// hadronic events)
///
/// . SM_Et: Et (not boost invariant, reduces to mt at zero rapidity and
/// to pt and infinite rapidity)
///
/// . SM_mt: transverse mass = sqrt(m^2+pt^2)
///
CDFMidPointPlugin (
double seed_threshold_in ,
double cone_radius_in ,
double cone_area_fraction_in ,
int max_pair_size_in ,
int max_iterations_in ,
double overlap_threshold_in ,
SplitMergeScale sm_scale_in = SM_pt) :
_seed_threshold (seed_threshold_in ),
_cone_radius (cone_radius_in ),
_cone_area_fraction (cone_area_fraction_in ),
_max_pair_size (max_pair_size_in ),
_max_iterations (max_iterations_in ),
_overlap_threshold (overlap_threshold_in ),
_sm_scale (sm_scale_in) {}
/// a compact constructor
///
/// NB: as of version 2.4, the default value for the
/// overlap_threshold threshold has been removed, to avoid
/// misleading people into using the value of 0.5 without thinking,
/// which is known to have adverse effects in high-noise
/// environments. A recommended value is 0.75.
CDFMidPointPlugin (double cone_radius_in,
double overlap_threshold_in,// = 0.5,
double seed_threshold_in = 1.0,
double cone_area_fraction_in = 1.0) :
_seed_threshold (seed_threshold_in ),
_cone_radius (cone_radius_in ),
_cone_area_fraction (cone_area_fraction_in ),
_max_pair_size (2 ),
_max_iterations (100 ),
_overlap_threshold (overlap_threshold_in ),
_sm_scale (SM_pt) {}
// some functions to return info about parameters
double seed_threshold () const {return _seed_threshold ;}
double cone_radius () const {return _cone_radius ;}
double cone_area_fraction () const {return _cone_area_fraction ;}
int max_pair_size () const {return _max_pair_size ;}
int max_iterations () const {return _max_iterations ;}
double overlap_threshold () const {return _overlap_threshold ;}
// the things that are required by base class
virtual std::string description () const;
virtual void run_clustering(ClusterSequence &) const;
/// the plugin mechanism's standard way of accessing the jet radius
virtual double R() const {return cone_radius();}
private:
double _seed_threshold ;
double _cone_radius ;
double _cone_area_fraction;
int _max_pair_size ;
int _max_iterations ;
double _overlap_threshold ;
SplitMergeScale _sm_scale ;
static thread_safety_helpers::FirstTimeTrue _first_time;
/// print a banner for reference to the 3rd-party code
void _print_banner(std::ostream *ostr) const;
};
FASTJET_END_NAMESPACE // defined in fastjet/internal/base.hh
#endif // __CDFMIDPOINTPLUGIN_HH__
fastjet::CDFMidPointPlugin::SplitMergeScale
SplitMergeScale
the choice of scale to be used in the split-merge step
Definition CDFMidPointPlugin.hh:73
fastjet::CDFMidPointPlugin::R
virtual double R() const
the plugin mechanism's standard way of accessing the jet radius
Definition CDFMidPointPlugin.hh:163
fastjet::CDFMidPointPlugin::CDFMidPointPlugin
CDFMidPointPlugin(double cone_radius_in, double overlap_threshold_in, double seed_threshold_in=1.0, double cone_area_fraction_in=1.0)
a compact constructor
Definition CDFMidPointPlugin.hh:137
fastjet::CDFMidPointPlugin::CDFMidPointPlugin
CDFMidPointPlugin(double seed_threshold_in, double cone_radius_in, double cone_area_fraction_in, int max_pair_size_in, int max_iterations_in, double overlap_threshold_in, SplitMergeScale sm_scale_in=SM_pt)
A CDFMidPointPlugin constructor that looks like the one provided by CDF.
Definition CDFMidPointPlugin.hh:114
fastjet::JetDefinition::Plugin
a class that allows a user to introduce their own "plugin" jet finder
Definition JetDefinition.hh:560
fastjet::thread_safety_helpers::FirstTimeTrue
provides an object wich will return "true" the first time () is called and false afterwards
Definition thread_safety_helpers.hh:231