| 1 | // $Id: SoftDrop.cc 1059 2017-09-07 20:48:00Z gsoyez $
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| 2 | //
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| 3 | // Copyright (c) 2014-, Gregory Soyez, Jesse. Thaler
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| 4 | // based on arXiv:1402.2657 by Andrew J. Larkoski, Simone Marzani,
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| 5 | // Gregory Soyez, Jesse Thaler
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| 6 | //
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| 7 | //----------------------------------------------------------------------
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| 8 | // This file is part of FastJet contrib.
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| 9 | //
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| 10 | // It is free software; you can redistribute it and/or modify it under
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| 11 | // the terms of the GNU General Public License as published by the
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| 12 | // Free Software Foundation; either version 2 of the License, or (at
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| 13 | // your option) any later version.
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| 14 | //
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| 15 | // It is distributed in the hope that it will be useful, but WITHOUT
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| 16 | // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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| 17 | // or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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| 18 | // License for more details.
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| 19 | //
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| 20 | // You should have received a copy of the GNU General Public License
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| 21 | // along with this code. If not, see <http://www.gnu.org/licenses/>.
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| 22 | //----------------------------------------------------------------------
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| 23 |
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| 24 | #include "SoftDrop.hh"
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| 25 | #include <cmath>
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| 26 | #include <sstream>
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| 27 |
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| 28 | using namespace std;
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| 29 |
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| 30 | FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
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| 31 |
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| 32 | namespace contrib{
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| 33 |
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| 34 | //----------------------------------------------------------------------
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| 35 | // TODO:
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| 36 | //
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| 37 | // - implement reclustering (at the moment we assume it's C/A as for mMDT
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| 38 | //
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| 39 | // - what is returned if no substructure is found? [and for negativeve
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| 40 | // pt, m2 or other situations where mMDT currentlty returns an empty
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| 41 | // PseudoJet]
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| 42 | //
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| 43 | // GS.: mMDT seeks substructure so it makes sense for it to return
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| 44 | // an empry PseudoJet when no substructure is found (+ it is the
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| 45 | // original behaviour). For SoftDrop, in grooming mode (beta>0), if
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| 46 | // would make sense to return a jet with a single particle. In
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| 47 | // tagging mode (beta<0), the situation is less clear. At the level
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| 48 | // of the implementation, having a virtual function could work
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| 49 | // (with a bit of care to cover the -ve pt or m2 cases)
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| 50 | //
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| 51 | // - Do we include Andrew and Simone in the "contrib-author" list
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| 52 | // since they are on the paper? Do we include Gavin in the author's
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| 53 | // list since he started this contrib?
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| 54 | //
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| 55 | //----------------------------------------------------------------------
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| 56 |
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| 57 | //----------------------------------------------------------------------
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| 58 | double SoftDrop::symmetry_cut_fn(const PseudoJet & p1,
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| 59 | const PseudoJet & p2,
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| 60 | void *optional_R0sqr_ptr) const{
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| 61 | double R0sqr = (optional_R0sqr_ptr == 0) ? _R0sqr : *((double*) optional_R0sqr_ptr);
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| 62 | return _symmetry_cut * pow(squared_geometric_distance(p1,p2)/R0sqr, 0.5*_beta);
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| 63 | }
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| 64 |
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| 65 | //----------------------------------------------------------------------
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| 66 | string SoftDrop::symmetry_cut_description() const {
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| 67 | ostringstream ostr;
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| 68 | ostr << _symmetry_cut << " (theta/" << sqrt(_R0sqr) << ")^" << _beta << " [SoftDrop]";
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| 69 | return ostr.str();
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| 70 | }
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| 71 |
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| 72 | } // namespace contrib
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| 73 |
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| 74 | FASTJET_END_NAMESPACE
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