Rivet analyses

Cross section for e+e− → π0π0γ at energies between 0.6 and 0.97 GeV.

Experiment: CMD2 (VEPP-2M)

Inspire ID: 630009

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B580 (2004) 119-128, 2004

Beams: e+ e-

Beam energies: (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5)GeV

Run details: - e+e- to hadrons

Measurement of the cross section for e+e− → π0π0γ at energies between 0.6 and 0.97 GeV.

Source code:CMD2_2004_I630009.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class CMD2_2004_I630009 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_2004_I630009);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(FinalState(), "FS");
      book(_numPiPiGamma, 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      const FinalState& fs = apply<FinalState>(event, "FS");

      map<long, int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
        nCount[p.pid()] += 1;
        ++ntotal;
      }
      // three particles (pi0 pi0 gamma)
      if (ntotal != 3) vetoEvent;
      if (nCount[111] == 2 && nCount[22] == 1) _numPiPiGamma->fill(round(sqrtS() / MeV));
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_numPiPiGamma, crossSection() / sumOfWeights() / picobarn);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<int> _numPiPiGamma;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CMD2_2004_I630009);


}