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## Rivet analyses reference

### ALICE_2010_I880049

Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 2.76$ TeV
Experiment: ALICE (LHC)
Inspire ID: 880049
Status: VALIDATED
Authors:
• Przemyslaw Karczmarczyk
• Jan Fiete Grosse-Oetringhaus
• Jochen Klein
References:
Beams: 1000822080 1000822080
Beam energies: (287040.0, 287040.0) GeV
No run details listed

The centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.

Source code: ALICE_2010_I880049.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 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/ChargedFinalState.hh" #include "Rivet/Tools/Cuts.hh" #include "Rivet/Projections/SingleValueProjection.hh" #include "Rivet/Tools/AliceCommon.hh" #include "Rivet/Projections/AliceCommon.hh" #include "Rivet/Projections/HepMCHeavyIon.hh" namespace Rivet { /// @brief ALICE PbPb at 2.76 TeV multiplicity at mid-rapidity class ALICE_2010_I880049 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(ALICE_2010_I880049); /// @name Analysis methods //@{ /// Book histograms and initialise projections before the run void init() { // Declare centrality projection declareCentrality(ALICE::V0MMultiplicity(), "ALICE_2015_PBPBCentrality", "V0M", "V0M"); // Trigger projections declare(ChargedFinalState((Cuts::eta > 2.8 && Cuts::eta < 5.1) && Cuts::pT > 0.1*GeV), "VZERO1"); declare(ChargedFinalState((Cuts::eta > -3.7 && Cuts::eta < -1.7) && Cuts::pT > 0.1*GeV), "VZERO2"); declare(ChargedFinalState(Cuts::abseta < 1. && Cuts::pT > 0.15*GeV), "SPD"); // Charged, primary particles with |eta| < 0.5 and pT > 50 MeV declare(ALICE::PrimaryParticles(Cuts::abseta < 0.5 && Cuts::pT > 50*MeV && Cuts::abscharge > 0), "APRIM"); // Access the HepMC heavy ion info declare(HepMCHeavyIon(), "HepMC"); // Histograms and variables initialization book(_histNchVsCentr, 1, 1, 1); book(_histNpartVsCentr, 1, 1, 2); } /// Perform the per-event analysis void analyze(const Event& event) { // Charged, primary particles with at least pT = 50 MeV // in eta range of |eta| < 0.5 Particles chargedParticles = applyProjection(event,"APRIM").particles(); // Trigger projections const ChargedFinalState& vz1 = applyProjection(event,"VZERO1"); const ChargedFinalState& vz2 = applyProjection(event,"VZERO2"); const ChargedFinalState& spd = applyProjection(event,"SPD"); int fwdTrig = (vz1.particles().size() > 0 ? 1 : 0); int bwdTrig = (vz2.particles().size() > 0 ? 1 : 0); int cTrig = (spd.particles().size() > 0 ? 1 : 0); if (fwdTrig + bwdTrig + cTrig < 2) vetoEvent; const CentralityProjection& centrProj = apply(event, "V0M"); double centr = centrProj(); if (centr > 80) vetoEvent; // Calculate number of charged particles and fill histogram double nch = chargedParticles.size(); _histNchVsCentr->fill(centr, nch); // Attempt to extract Npart form GenEvent. if (event.genEvent()->heavy_ion()) { const HepMCHeavyIon & hi = apply(event, "HepMC"); _histNpartVsCentr->fill(centr, hi.Npart_proj() + hi.Npart_targ()); } } /// Normalise histograms etc., after the run //void finalize() { } //@} private: /// @name Histograms //@{ Profile1DPtr _histNchVsCentr; Profile1DPtr _histNpartVsCentr; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(ALICE_2010_I880049); }