Rivet analyses

Charged particle production as function of centrality, peripheral events only, in PbPb collisions at 2.76 TeV.

Experiment: ALICE (LHC)

Inspire ID: 1394676

Status: UNVALIDATED

Authors: - Christian Bierlich

References: - Phys.Lett.B754(2016)373-385 - DOI:10.1016/j.physletb.2015.12.082” - arXiv: 1509.07299

Beams: 1000822080 1000822080

Beam energies: (287040.0, 287040.0)GeV

Run details: - PbPb minimum bias events. The analysis holds the Primary Particle definition, so don’t limit decays on generator level.

Charged particle pseudorapidity density in centrality classes 30-40, 40-50, 50-60, 60-70, 70-80, 80-90. Measurements cover a wide η range from -3.5 to 5. Centrality classes refer to forward V0 spectrum, as also measured by ALICE, can be modified to use a user definition instead.

Source code:ALICE_2016_I1394676.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Analyses/AliceCommon.hh"
#include "Rivet/Projections/ChargedFinalState.hh"

namespace Rivet {


  /// @brief ALICE PbPb at 2.76 TeV eta distributions, peripheral events.
  class ALICE_2016_I1394676 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ALICE_2016_I1394676);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      // Centrality projection.
      declareCentrality(ALICE::V0MMultiplicity(), "ALICE_2015_CENT_PBPB", "V0M", "V0M");
      // Projections for the 2-out-of-3 trigger.
      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");

      // Primary particles.
      declare(ALICE::PrimaryParticles(Cuts::abseta < 5.6), "APRIM");

      // The centrality bins and the corresponding histograms and sow counters.
      centralityBins = {40, 50, 60, 70, 80, 90};
      for (int i = 0, N = centralityBins.size(); i < N; ++i) {
        book(histEta[centralityBins[i]], 1, 1, i + 1);
        book(sow[centralityBins[i]], "sow_" + toString(i));
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Trigger projections.
      const ChargedFinalState& vz1 = apply<ChargedFinalState>(event, "VZERO1");
      const ChargedFinalState& vz2 = apply<ChargedFinalState>(event, "VZERO2");
      const ChargedFinalState& spd = apply<ChargedFinalState>(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& cent = apply<CentralityProjection>(event, "V0M");
      double c = cent();
      // No centralities below 30 %
      if (c < 30.) return;
      // Find the correct centrality histogram
      auto hItr = histEta.upper_bound(c);
      if (hItr == histEta.end()) return;
      // Find the correct sow.
      auto sItr = sow.upper_bound(c);
      if (sItr == sow.end()) return;
      sItr->second->fill();

      // Fill the histograms.
      for (const auto& p : apply<ALICE::PrimaryParticles>(event, "APRIM").particles())
        if (p.abscharge() > 0) hItr->second->fill(p.eta());
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      for (int i = 0, N = centralityBins.size(); i < N; ++i)
        histEta[centralityBins[i]]->scaleW(1. / sow[centralityBins[i]]->sumW());
    }

    /// @}


    /// @name Histograms
    /// @{
    vector<double> centralityBins;
    map<double, Histo1DPtr> histEta;
    map<double, CounterPtr> sow;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ALICE_2016_I1394676);


}