Rivet analyses

Beam energy dependence of the third harmonic of azimuthal correlations

Experiment: STAR (RHIC)

Inspire ID: 1414638

Status: UNVALIDATED

Authors: - Maria Stefaniak - Christian Bierlich

References: - Phys.Rev.Lett. 116 (2016) no.11, 112302 - DOI: 10.1103/PhysRevLett.116.112302 - arXiv: 1601.01999

Beams: 1000791970 1000791970

Beam energies: (758.5, 758.5); (1132.8, 1132.8); (1428.2, 1428.2); (1930.6, 1930.6); (2659.5, 2659.5); (3841.5, 3841.5); (6146.4, 6146.4); (19700.0, 19700.0)GeV

Run details: - Minimum bias AuAu events at various collision energies.

Results of harmonic decomposition of two-particle azimuthal correlations in AuAu collisions, in energies recorded in the beam energy scan. For MC purposes, note that the lowest energies might be too low for standard generators to even initialise.

Source code:STAR_2016_I1414638.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/SingleValueProjection.hh"
#include "Rivet/Projections/ImpactParameterProjection.hh"
#include "Rivet/Tools/Percentile.hh"
#include "Rivet/Analyses/RHICCommon.hh"

namespace Rivet {


  /// @brief Third harmonic of azimuthal correlations in Au+Au collisions at different COM energies
  class STAR_2016_I1414638 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(STAR_2016_I1414638);


    void init() {
      /// Projections
      declareCentrality(STAR_BES_Centrality(), "STAR_BES_CALIB", "CMULT", "CMULT");
      declare(ChargedFinalState(Cuts::abseta < 1.0 && Cuts::pT > 0.2*GeV), "CFS");

      // Histograms
      size_t ih = 0;
      for (double eVal : allowedEnergies()) {
        const int en = round(eVal/MeV);
        if (isCompatibleWithSqrtS(eVal))  _sqs = en;
        for (size_t i=1; i <= cenAxis.numBins(); ++i) {
          book(h_v32[en+i], 1+i+9*ih, 1, 1);
        }
        ++ih;
      }
      raiseBeamErrorIf(_sqs == 0);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
      // Require at least two charged particles for the analysis to make sense.
      // No further triggers are described in the paper.
      const Particles& particles = cfs.particles();
      if (particles.size() < 2) return;
      // The centrality projection
      const CentralityProjection& cent = apply<CentralityProjection>(event,"CMULT");
      const double c = cent();
      // Find the correct histogram to fill.
      size_t idx = cenAxis.index(c);
      if (!idx || idx > cenAxis.numBins())  vetoEvent;
      for (int i = 0, N = particles.size(); i < N; ++i){
        for (int j = i + 1; j < N; ++j) {
          const double eta1 = particles[i].eta();
          const double eta2 = particles[j].eta();
          if (eta1 * eta2 < 0) {
            const double deltaPhi = abs(particles[i].phi() - particles[j].phi());
            // Fill profile with v_2(2)^2 from eq. (1) in the paper.
            h_v32[_sqs+idx]->fill(abs(eta1 - eta2), cos(3.*deltaPhi));
          }
        }
      }
    }

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

    /// @}


    /// @name Bin edges
    /// @{
    /// The centrality bins
    YODA::Axis<double> cenAxis = YODA::Axis<double>({5., 10., 20., 30., 40., 50., 60., 70., 80.});
    /// The analysis energies
    const doubles energies = {7.7, 11.5, 14.5, 19.6, 27.0, 39.0, 62.4, 200.0};
    /// @}


    /// The histograms
    map<double, Profile1DPtr> h_v32;

    int _sqs = 0;

  };


  RIVET_DECLARE_PLUGIN(STAR_2016_I1414638);

}