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ATLAS_2012_I1124167

Measurement of charged-particle event shape variables
Experiment: ATLAS (LHC)
Inspire ID: 1124167
Status: VALIDATED
Authors:
• Deepak Kar
References:
• arXiv: 1207.6915
• Phys.Rev. D88 (2013) 032004
• 10.1103/PhysRevD.88.032004
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
• Minimum bias events with at least 6 charged particles at 7 TeV

The measurement of charged-particle event shape variables is presented in inclusive inelastic $pp$ collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state charged particles momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged-particle transverse momentum, charged-particle multiplicity, and summed transverse momentum is presented.

Source code: ATLAS_2012_I1124167.cc
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/ChargedFinalState.hh" #include "Rivet/Projections/FinalState.hh" #include "Rivet/Projections/Thrust.hh" #include "Rivet/Projections/Sphericity.hh" namespace Rivet { /// Rivet analysis class for ATLAS min bias event shapes class ATLAS_2012_I1124167 : public Analysis { public: /// Constructor ATLAS_2012_I1124167() : Analysis("ATLAS_2012_I1124167") { } /// Initialization, called once before running void init() { // Projections ChargedFinalState cfs(Cuts::abseta < 2.5 && Cuts::pT > 0.5*GeV); declare(cfs, "CFS"); // Book histograms book(_hist_T_05_25 ,1,1,1); book(_hist_T_05 ,2,1,1); book(_hist_T_25_50 ,1,1,2); book(_hist_T_25 ,2,1,2); book(_hist_T_50_75 ,1,1,3); book(_hist_T_50 ,2,1,3); book(_hist_T_75_100,1,1,4); book(_hist_T_75 ,2,1,4); book(_hist_T_100 ,2,1,5); book(_hist_TM_05_25 ,3,1,1); book(_hist_TM_05 ,4,1,1); book(_hist_TM_25_50 ,3,1,2); book(_hist_TM_25 ,4,1,2); book(_hist_TM_50_75 ,3,1,3); book(_hist_TM_50 ,4,1,3); book(_hist_TM_75_100,3,1,4); book(_hist_TM_75 ,4,1,4); book(_hist_TM_100 ,4,1,5); book(_hist_S_05_25 ,5,1,1); book(_hist_S_05 ,6,1,1); book(_hist_S_25_50 ,5,1,2); book(_hist_S_25 ,6,1,2); book(_hist_S_50_75 ,5,1,3); book(_hist_S_50 ,6,1,3); book(_hist_S_75_100,5,1,4); book(_hist_S_75 ,6,1,4); book(_hist_S_100 ,6,1,5); book(_hist_T_N ,7,1,1); book(_hist_TM_N ,7,1,2); book(_hist_S_N ,7,1,3); book(_hist_T_S ,8,1,1); book(_hist_TM_S ,8,1,2); book(_hist_S_S ,8,1,3); } void analyze(const Event& event) { const double weight = 1.0; // CFS projection and particles const Particles& particles500 = apply(event, "CFS").particlesByPt(); // Require at least 6 charged particles if (particles500.size() < 6) vetoEvent; // Preparation for Thrust calculation vector momenta; // Counters double num500 = 0; double ptSum500 = 0; double pTlead = particles500[0].pT()/GeV; // Loop over particles for (const Particle& p : particles500) { num500 += 1; ptSum500 += p.pT()/GeV; // Transverse Thrust calculation requires p_z to be set to 0 Vector3 mom = p.p3(); mom.setZ(0.0); momenta.push_back(mom); } // If only 2 particles, we need to use a ghost so that Thrust.calc() doesn't return 1. if (momenta.size() == 2) { momenta.push_back(Vector3(1e-10*MeV, 0., 0.)); } // Actual thrust calculation Thrust thrust; thrust.calc(momenta); const double T = 1.0 - thrust.thrust(); const double TM = thrust.thrustMajor(); Sphericity sphericity; sphericity.calc(momenta); double S = sphericity.transSphericity(); if ( std::isnan(S) ) S = -1.0; // put this in the underflow bin // Fill histos, most inclusive first // pTlead > 0.5 _hist_T_05->fill(T , weight); _hist_TM_05->fill(TM, weight); _hist_S_05->fill(S , weight); // pTlead 0.5 - 2.5 if (pTlead <= 2.5) { _hist_T_05_25->fill(T , weight); _hist_TM_05_25->fill(TM, weight); _hist_S_05_25->fill(S , weight); } // pTlead > 2.5 if (pTlead > 2.5) { _hist_T_25->fill(T , weight); _hist_TM_25->fill(TM, weight); _hist_S_25->fill(S , weight); } // pTlead 2.5 - .5 if (inRange(pTlead, 2.5, 5.0)) { _hist_T_25_50->fill(T , weight); _hist_TM_25_50->fill(TM, weight); _hist_S_25_50->fill(S , weight); } // pTlead > 5 if (pTlead > 5) { _hist_T_50->fill(T , weight); _hist_TM_50->fill(TM, weight); _hist_S_50->fill(S , weight); } // pTlead 5 - 7.5 if (inRange(pTlead, 5.0, 7.5)) { _hist_T_50_75->fill(T , weight); _hist_TM_50_75->fill(TM, weight); _hist_S_50_75->fill(S , weight); } // pTlead > 7.5 if (pTlead > 7.5) { _hist_T_75->fill(T , weight); _hist_TM_75->fill(TM, weight); _hist_S_75->fill(S , weight); } // pTlead 7.5 - 10 if (inRange(pTlead, 7.5, 10)) { _hist_T_75_100->fill(T , weight); _hist_TM_75_100->fill(TM, weight); _hist_S_75_100->fill(S , weight); } // pTlead > 10 if (pTlead > 10) { _hist_T_100->fill(T , weight); _hist_TM_100->fill(TM, weight); _hist_S_100->fill(S , weight); } // Profiles Nch vs. ES _hist_T_N->fill(num500, T, weight); _hist_TM_N->fill(num500, TM, weight); _hist_S_N->fill(num500, S, weight); // Profiles pTsum vs. ES _hist_T_S->fill(ptSum500, T, weight); _hist_TM_S->fill(ptSum500, TM, weight); _hist_S_S->fill(ptSum500, S, weight); } void finalize() { normalize(_hist_T_05_25); normalize(_hist_T_05); normalize(_hist_T_25_50); normalize(_hist_T_25); normalize(_hist_T_50_75); normalize(_hist_T_50); normalize(_hist_T_75_100); normalize(_hist_T_75); normalize(_hist_T_100); normalize(_hist_TM_05_25); normalize(_hist_TM_05); normalize(_hist_TM_25_50); normalize(_hist_TM_25); normalize(_hist_TM_50_75); normalize(_hist_TM_50); normalize(_hist_TM_75_100); normalize(_hist_TM_75); normalize(_hist_TM_100); normalize(_hist_S_05_25); normalize(_hist_S_05); normalize(_hist_S_25_50); normalize(_hist_S_25); normalize(_hist_S_50_75); normalize(_hist_S_50); normalize(_hist_S_75_100); normalize(_hist_S_75); normalize(_hist_S_100); } private: Histo1DPtr _hist_T_05_25, _hist_T_05, _hist_T_25_50, _hist_T_25, _hist_T_50_75, _hist_T_50, _hist_T_75_100, _hist_T_75, _hist_T_100; Histo1DPtr _hist_TM_05_25, _hist_TM_05, _hist_TM_25_50, _hist_TM_25, _hist_TM_50_75, _hist_TM_50, _hist_TM_75_100, _hist_TM_75, _hist_TM_100; Histo1DPtr _hist_S_05_25, _hist_S_05, _hist_S_25_50, _hist_S_25, _hist_S_50_75, _hist_S_50, _hist_S_75_100, _hist_S_75, _hist_S_100; Profile1DPtr _hist_T_N, _hist_TM_N, _hist_S_N; Profile1DPtr _hist_T_S, _hist_TM_S, _hist_S_S; }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(ATLAS_2012_I1124167); }