[4d3fb73] | 1 | /*
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| 2 | * Delphes: a framework for fast simulation of a generic collider experiment
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| 3 | * Copyright (C) 2012-2014 Universite catholique de Louvain (UCL), Belgium
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| 4 | *
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| 5 | * This program is free software: you can redistribute it and/or modify
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| 6 | * it under the terms of the GNU General Public License as published by
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| 7 | * the Free Software Foundation, either version 3 of the License, or
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| 8 | * (at your option) any later version.
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| 9 | *
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| 10 | * This program is distributed in the hope that it will be useful,
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| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | * GNU General Public License for more details.
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| 14 | *
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| 15 | * You should have received a copy of the GNU General Public License
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| 16 | * along with this program. If not, see <http://www.gnu.org/licenses/>.
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| 17 | */
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| 18 |
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| 19 | /** \class DecayFilter
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| 20 | *
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| 21 | * This module randomly generates decays along the particle trajectory length
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| 22 | * according to actual particle decay length, taking into account for the boost
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| 23 | * and using ROOT TDatabasePDG as a source for the particle lifetime.
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| 24 | *
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| 25 | * This module is to to be used after a PropagateParticle step or a similar module
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| 26 | * that calculates and store a trajectory length.
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| 27 | *
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| 28 | * Particles that decay are not added to the OutputArray.
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| 29 | *
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| 30 | * \author R. Preghenella - INFN, Bologna
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| 31 | *
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| 32 | */
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| 33 |
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| 34 | #include "modules/DecayFilter.h"
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| 35 |
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| 36 | #include "classes/DelphesClasses.h"
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| 37 | #include "classes/DelphesFactory.h"
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| 38 | #include "classes/DelphesFormula.h"
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| 39 |
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| 40 | #include "ExRootAnalysis/ExRootClassifier.h"
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| 41 | #include "ExRootAnalysis/ExRootFilter.h"
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| 42 | #include "ExRootAnalysis/ExRootResult.h"
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| 43 |
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| 44 | #include "TDatabasePDG.h"
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| 45 | #include "TParticlePDG.h"
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| 46 | #include "TFormula.h"
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| 47 | #include "TLorentzVector.h"
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| 48 | #include "TMath.h"
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| 49 | #include "TObjArray.h"
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| 50 | #include "TRandom3.h"
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| 51 | #include "TString.h"
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| 52 |
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| 53 | #include <algorithm>
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| 54 | #include <iostream>
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| 55 | #include <sstream>
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| 56 | #include <stdexcept>
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| 57 |
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| 58 | using namespace std;
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| 59 |
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| 60 | //------------------------------------------------------------------------------
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| 61 |
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| 62 | DecayFilter::DecayFilter() :
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| 63 | fItInputArray(0)
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| 64 | {}
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| 65 |
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| 66 | //------------------------------------------------------------------------------
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| 67 |
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| 68 | DecayFilter::~DecayFilter()
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| 69 | {}
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| 70 |
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| 71 | //------------------------------------------------------------------------------
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| 72 |
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| 73 | void DecayFilter::Init()
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| 74 | {
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| 75 |
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| 76 | // import input array(s)
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| 77 |
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| 78 | fInputArray = ImportArray(GetString("InputArray", "FastJetFinder/jets"));
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| 79 | fItInputArray = fInputArray->MakeIterator();
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| 80 |
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| 81 | // create output array(s)
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| 82 |
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| 83 | fOutputArray = ExportArray(GetString("OutputArray", "tracks"));
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| 84 | }
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| 85 |
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| 86 | //------------------------------------------------------------------------------
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| 87 |
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| 88 | void DecayFilter::Finish()
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| 89 | {
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| 90 | if(fItInputArray) delete fItInputArray;
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| 91 | }
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| 92 |
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| 93 | //------------------------------------------------------------------------------
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| 94 |
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| 95 | void DecayFilter::Process()
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| 96 | {
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| 97 | Candidate *candidate;
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| 98 | TDatabasePDG *pdgdb = TDatabasePDG::Instance();
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| 99 | const Double_t c = TMath::C(); // [m/s]
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| 100 | Double_t m, t, p, bgct, L, l;
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| 101 | Bool_t hasDecayed = kFALSE;
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| 102 |
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| 103 | // loop over all input candidates
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| 104 | fItInputArray->Reset();
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| 105 | while((candidate = static_cast<Candidate *>(fItInputArray->Next())))
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| 106 | {
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| 107 | // get particle information from PDG
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| 108 | TParticlePDG *pdg = pdgdb->GetParticle(candidate->PID);
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| 109 | if (!pdg) { // don't know this particle
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| 110 | fOutputArray->Add(candidate);
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| 111 | continue;
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| 112 | }
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| 113 | m = pdg->Mass();
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| 114 | t = pdg->Lifetime(); // [s]
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| 115 | if (t == 0.) { // does not decay
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| 116 | fOutputArray->Add(candidate);
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| 117 | continue;
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| 118 | }
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| 119 |
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| 120 | // compute boosted decay length (beta gamma c tau)
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| 121 | p = candidate->P;
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| 122 | bgct = p / m * c * t; // [m]
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| 123 |
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| 124 | // get full trajectory length and generate random decay length
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| 125 | L = candidate->L * 1.0E-3; // [m]
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| 126 | l = gRandom->Exp(bgct);
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| 127 |
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| 128 | // if random decay happens before end of trajectory, reject track
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| 129 | if (l < L) continue;
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| 130 |
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| 131 | // else particle did not decay within the trajectory
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| 132 | fOutputArray->Add(candidate);
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| 133 | }
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| 134 | }
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| 135 |
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| 136 | //------------------------------------------------------------------------------
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