Rivet analyses

Cross section for e+e− → π+π− between 1.35 and 2.4 GeV

Experiment: DM2 (DCI)

Inspire ID: 267118

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B220 (1989) 321-327, 1989

Beams: e+ e-

Beam energies: (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.8, 0.8); (0.8, 0.8); (0.8, 0.8); (0.8, 0.8); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.1, 1.1)GeV

Run details: - e+ e- to hadrons

Measurement of the cross section for e+e− → π+π− at energies between 1.35 and 2.4 GeV. Useful for comparing models of the pion form factor.

Source code:DM2_1989_I267118.cc

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


namespace Rivet {


  /// @brief e+e- > pi+pi-
  class DM2_1989_I267118 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(DM2_1989_I267118);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");

      // Book histograms
      book(_npion,1,1,1);
      for (const string& en : _npion.binning().edges<0>()) {
        double eval = stod(en)*GeV;
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en; break;
        }
      }
      raiseBeamErrorIf(_sqs.empty());
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      if (fs.particles().size()!=2) vetoEvent;
      for (const Particle& p : fs.particles()) {
        if (p.abspid() != PID::PIPLUS) vetoEvent;
      }
      _npion->fill(_sqs);
    }


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

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _npion;
    string _sqs = "";
    /// @}


  };


  RIVET_DECLARE_PLUGIN(DM2_1989_I267118);
}