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BABAR_2017_I1621593

$e^+e^-\to \pi^+\pi^-\pi^0\pi^0$ cross section from 0.85 to 4.5 GeV
Experiment: BABAR (PEP-II)
Inspire ID: 1621593
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D96 (2017) no.9, 092009
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$ between 0.85 to 4.5 GeV using radiative return.

Source code: BABAR_2017_I1621593.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/FinalState.hh"


namespace Rivet {


  /// @brief Add a short analysis description here
  class BABAR_2017_I1621593 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BABAR_2017_I1621593);


    /// @name Analysis methods
    //@{

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

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

      book(_num4pi,   "TMP/num4");
      book(_numOmega, "TMP/numOmega");
      _mult.resize(2);
      book(_mult[0], 1, 1, 1);
      book(_mult[1], 2, 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;
      }
      if(ntotal!=4) vetoEvent;
      if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==2) {
        _num4pi->fill();
        const FinalState& ufs = apply<FinalState>(event, "UFS");
        if (!ufs.particles(Cuts::pid==223).empty()) {
          _numOmega->fill();
        }
      }

    }


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

      for(size_t ix=1;ix<3;++ix) {
        double sigma,error;
        if(ix==1) {
          sigma = _num4pi->val();
          error = _num4pi->err();
        }
        else {
          sigma = _numOmega->val();
          error = _numOmega->err();
        }
        sigma *= crossSection()/ sumOfWeights() /nanobarn;
        error *= crossSection()/ sumOfWeights() /nanobarn; 
        Scatter2D temphisto(refData(ix, 1, 1));
        for (size_t b = 0; b < temphisto.numPoints(); b++) {
          const double x  = temphisto.point(b).x();
          pair<double,double> ex = temphisto.point(b).xErrs();
          pair<double,double> ex2 = ex;
          if(ex2.first ==0.) ex2. first=0.0001;
          if(ex2.second==0.) ex2.second=0.0001;
          if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
            _mult[ix-1]->addPoint(x, sigma, ex, make_pair(error,error));
          }
          else {
            _mult[ix-1]->addPoint(x, 0., ex, make_pair(0.,.0));
          }
        }
      }
    }

    //@}

    /// @name Histograms
    //@{
    CounterPtr _num4pi, _numOmega;
    vector<Scatter2DPtr> _mult;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BABAR_2017_I1621593);


}