Rivet analyses

Cross section for e+e− → πγ for energies between 600 MeV and 970 MeV

Experiment: SND (VEPP-2M)

Inspire ID: 612867

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys. Lett. B559, 171 (2003)

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons below 0.6 and 1.38 GeV

Cross section for e+e− → πγ for energies between 600 MeV and 970 MeV

Source code:SND_2003_I612867.cc

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


namespace Rivet {


  /// @brief Add a short analysis description here
  class SND_2003_I612867 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2003_I612867);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      book(_numPi0Gamma, "TMP/Pi0Gamma");
    }


    /// 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;
      }
      if(ntotal==2 && nCount[22]==1 && nCount[111]==1)
    _numPi0Gamma->fill();

    }


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

      double sigma = _numPi0Gamma->val();
      double error = _numPi0Gamma->err();
      sigma *= crossSection()/ sumOfWeights() /nanobarn;
      error *= crossSection()/ sumOfWeights() /nanobarn;
      Estimate1DPtr mult;
      book(mult, 1, 1, 1);
      for (auto& b : mult->bins()) {
        if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
          b.set(sigma, error);
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    CounterPtr _numPi0Gamma;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(SND_2003_I612867);


}