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STAR_2016_I1414638

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 initialize.

Source code: STAR_2016_I1414638.cc
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// -*- 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/Tools/RHICCommon.hh"
#include <complex>

namespace Rivet {

  /// @brief Third harmonic of azimuthal correlations in Au+Au collisions 
  //  at different COM energies.
  class STAR_2016_I1414638 : public Analysis {
  public: 
    /// Constructor	  
    STAR_2016_I1414638 () : Analysis("STAR_2016_I1414638") {}

    void init() {
	/// Projections
	/// The centrality projection. 
	declareCentrality(STAR_BES_Centrality(), 
	  "STAR_BES_CALIB", "CMULT", "CMULT");

	/// The observed particles.
    	declare(ChargedFinalState(Cuts::abseta < 1.0 &&
			       	   Cuts::pT > 0.2*GeV), "CFS");
	/// The centrality bins
	centralityBins = {5., 10, 20, 30, 40, 50, 60, 70, 80};
	/// The corresponding histograms for the different analysis energies.
	vector<double> energies = {7.7, 11.5, 14.5, 19.6, 27.0, 39.0, 
	  62.4, 200.0};
	int energy = -1;
	for (int i = 0, N = energies.size(); i < N; ++i) {
	  if (fuzzyEquals(sqrtS()/197./GeV,energies[i],1E-1)) energy = i;
	}
	if (energy == -1) MSG_ERROR("Incompatible beam energy!");
	for (int i = 0; i < 9; ++i)
	  book(h_v32[centralityBins[i]], 1 + i + 9 * energy, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const ChargedFinalState& cfs = applyProjection<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.
      auto hItr = h_v32.upper_bound(c);
      if (hItr == h_v32.end()) return;
      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.
	    hItr->second->fill(abs(eta1 - eta2), cos(3.*deltaPhi));
          }
        }
       }
    }
    
    /// Normalise histograms etc., after the run
    void finalize() {
    
    }

    //@}


    /// @name Histograms
    //@{
    // The centralities.
    vector<double> centralityBins;
    // The histograms.
    map<double, Profile1DPtr> h_v32;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(STAR_2016_I1414638);

}