Rivet analyses

Cross section for e+e− → π+π+π−π+ between 0.89 and 1.1 GeV

Experiment: DM1 (ACO)

Inspire ID: 132828

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B81 (1979) 389-392, 1979

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for e+e− → π+π+π−π+ between 0.89 and 1.1 GeV

Source code:DM1_1979_I132828.cc

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

namespace Rivet {


  /// @brief e+e- -> pi+pi+pi-pi-
  class DM1_1979_I132828 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(DM1_1979_I132828);


    /// @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>()) {
        if (en == "-"s) {
          if (isCompatibleWithSqrtS(0.963)) {
            _sqs = en; break;
          }
          else if (isCompatibleWithSqrtS(0.985)) {
            _sqs = en; break;
          }
          else if (isCompatibleWithSqrtS(1.002)) {
            _sqs = en; break;
          }
          continue;
        }
        const size_t idx = en.find("-");
        if (idx == string::npos) {
          if (isCompatibleWithSqrtS(stod(en)*MeV)) {
            _sqs = en; break;
          }
          continue;
        }
        const double emin = stod(en.substr(0,idx))*MeV;
        const double emax = stod(en.substr(idx+1,string::npos))*MeV;
        if (inRange(sqrtS()/GeV, emin, emax)) {
          _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()!=4) 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(DM1_1979_I132828);
}