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KEDR_2019_I1673357

Measurement of $R$ between 1.84 and 3.72 GeV
Experiment: KEDR (VEPP-4M)
Inspire ID: 1673357
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B788 (2019) 42-51
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons and muon so the ratio can be computed

Measurement of $R$ for centre-of-mass energies between 1.84 and 3.72 GeV by the KEDR experiment.

Source code: KEDR_2019_I1673357.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {


  /// @brief Measurement of R
  class KEDR_2019_I1673357 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(KEDR_2019_I1673357);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");

      // Book histograms
      book(_c_hadrons, "/TMP/sigma_hadrons");
      book(_c_muons, "/TMP/sigma_muons");
    }


    /// 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;
      }
      // mu+mu- + photons
      if(nCount[-13]==1 and nCount[13]==1 &&
	 ntotal==2+nCount[22])
	_c_muons->fill();
      // everything else
      else
	_c_hadrons->fill();
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      Scatter1D R = *_c_hadrons/ *_c_muons;
      double              rval = R.point(0).x();
      pair<double,double> rerr = R.point(0).xErrs();
      double fact = crossSection()/ sumOfWeights() /picobarn;
      double sig_h = _c_hadrons->val()*fact;
      double err_h = _c_hadrons->err()*fact;
      double sig_m = _c_muons  ->val()*fact;
      double err_m = _c_muons  ->err()*fact;
      Scatter2D temphisto(refData(1, 1, 1));
      Scatter2DPtr hadrons;
      book(hadrons, "sigma_hadrons");
      Scatter2DPtr muons;
      book(muons, "sigma_muons"  );
      Scatter2DPtr mult1,mult2;
      book(mult1, 1, 1, 1);
      book(mult2, 1, 1, 2);
      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()/MeV, x-ex2.first, x+ex2.second)) {
          mult1   ->addPoint(x, rval, ex, rerr);
          mult2   ->addPoint(x, rval, ex, rerr);
          hadrons ->addPoint(x, sig_h, ex, make_pair(err_h,err_h));
          muons   ->addPoint(x, sig_m, ex, make_pair(err_m,err_m));
        }
        else {
          mult1   ->addPoint(x, 0., ex, make_pair(0.,.0));
          mult2   ->addPoint(x, 0., ex, make_pair(0.,.0));
          hadrons ->addPoint(x, 0., ex, make_pair(0.,.0));
          muons   ->addPoint(x, 0., ex, make_pair(0.,.0));
        }
      }
    }

    //@}


    /// @name Histograms
    //@{
    CounterPtr _c_hadrons, _c_muons;
    //@}


  };


  DECLARE_RIVET_PLUGIN(KEDR_2019_I1673357);

}