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// $Id: ModifiedMassDropTagger.hh 1032 2017-07-31 14:20:03Z gsoyez $
//
// Copyright (c) 2014-, Gavin P. Salam
// based on arXiv:1307.007 by Mrinal Dasgupta, Simone Marzani and Gavin P. Salam
//
//----------------------------------------------------------------------
// This file is part of FastJet contrib.
//
// It 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.
//
// It 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 this code. If not, see <http://www.gnu.org/licenses/>.
//----------------------------------------------------------------------
#ifndef __FASTJET_CONTRIB_MODIFIEDMASSDROPTAGGER_HH__
#define __FASTJET_CONTRIB_MODIFIEDMASSDROPTAGGER_HH__
#include "RecursiveSymmetryCutBase.hh"
FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
namespace contrib{
//------------------------------------------------------------------------
/// \class ModifiedMassDropTagger
/// An implementation of the modified Mass-Drop Tagger from arXiv:1307.0007.
///
class ModifiedMassDropTagger : public RecursiveSymmetryCutBase {
public:
/// Simplified constructor, which takes just a symmetry cut (applied
/// on the scalar_z variable) and an optional subtractor.
///
/// In this incarnation the ModifiedMassDropTagger is a bit of a
/// misnomer, because there is no mass-drop condition
/// applied. Recursion into the jet structure chooses the prong with
/// largest pt. (Results from arXiv:1307.0007 were based on the
/// largest mt, but this only makes a difference for values of the
/// symmetry_cut close to 1/2).
///
/// If the (optional) pileup subtractor can be supplied, then see
/// also the documentation for the set_input_jet_is_subtracted() member
/// function.
///
/// NB: The configuration of MMDT provided by this constructor is
/// probably the most robust for use with subtraction.
ModifiedMassDropTagger(double symmetry_cut,
const FunctionOfPseudoJet<PseudoJet> * subtractor = 0
) :
RecursiveSymmetryCutBase(scalar_z, // the default SymmetryMeasure
std::numeric_limits<double>::infinity(), // the default is no mass drop
larger_pt, // the default RecursionChoice
subtractor),
_symmetry_cut(symmetry_cut)
{}
/// Full constructor, which takes the following parameters:
///
/// \param symmetry_cut the value of the cut on the symmetry measure
/// \param symmetry_measure the choice of measure to use to estimate the symmetry
/// \param mu_cut the maximal allowed value of mass drop variable mu = m_heavy/m_parent
/// \param recursion_choice the strategy used to decide which subjet to recurse into
/// \param subtractor an optional pointer to a pileup subtractor (ignored if zero)
///
/// To obtain the mMDT as discussed in arXiv:1307.0007, use an
/// symmetry_measure that's one of the following
///
/// - RecursiveSymmetryCutBase::y (for a cut on y)
/// - RecursiveSymmetryCutBase::scalar_z (for a cut on z)
///
/// and use the default recursion choice of
/// RecursiveSymmetryCutBase::larger_pt (larger_mt will give something
/// very similar, while larger_m will give the behaviour of the
/// original, but now deprecated MassDropTagger)
///
/// Notes:
///
/// - By default the ModifiedMassDropTagger will relcuster the jets
/// with the C/A algorithm (if needed).
///
/// - the mu_cut parameter is mostly irrelevant when it's taken
/// larger than about 1/2: the tagger is then one that cuts
/// essentially on the (a)symmetry of the jet's momentum
/// sharing. The default value of infinity turns off its use
/// entirely
ModifiedMassDropTagger(double symmetry_cut,
SymmetryMeasure symmetry_measure,
double mu_cut = std::numeric_limits<double>::infinity(),
RecursionChoice recursion_choice = larger_pt,
const FunctionOfPseudoJet<PseudoJet> * subtractor = 0
) :
RecursiveSymmetryCutBase(symmetry_measure, mu_cut, recursion_choice, subtractor),
_symmetry_cut(symmetry_cut)
{}
/// default destructor
virtual ~ModifiedMassDropTagger(){}
//----------------------------------------------------------------------
// access to class info
double symmetry_cut() const { return _symmetry_cut; }
protected:
/// The symmetry cut function for MMDT returns just a constant, since the cut value
/// has no dependence on the subjet kinematics
virtual double symmetry_cut_fn(const PseudoJet & /* p1 */,
const PseudoJet & /* p2 */,
void *extra_parameters = 0
) const {return _symmetry_cut;}
virtual std::string symmetry_cut_description() const;
double _symmetry_cut;
};
} // namespace contrib
FASTJET_END_NAMESPACE
#endif // __FASTJET_CONTRIB_MODIFIEDMASSDROPTAGGER_HH__

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