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MARKI_1975_I100733

Measurement of $R$ and the hadronic cross section for energies between 2.4 and 6.9 GeV
Experiment: MARKI (Spear)
Inspire ID: 100733
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • https://doi.org/10.17182/hepdata.18759
Beams: e- e+
Beam energies: ANY
Run details:
  • e+ e- to hadrons and e+ e- to mu+ mu- (for normalization)

Measurement of $R$ and the hadronic cross section for energies between 2.4 and 6.9 GeV. The charged hadron spectum at 3, 4.8 and 7.4 GeV is also measured. The muonic cross sections is also outputted to the yoda file so that ratio $R$ can be recalcuated if runs are combined.

Source code: MARKI_1975_I100733.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class MARKI_1975_I100733 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(MARKI_1975_I100733);


    /// @name Analysis methods
    //@{

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

      declare(FinalState(), "FS");
      // Book histograms
      book(_c_hadrons, "/TMP/sigma_hadrons");
      book(_c_muons, "/TMP/sigma_muons");
    //   // if(inRange(sqrtS()/GeV,2.999,3.001))
    //     book(_h_charged, 3, 1, 1);
    //   // else if(inRange(sqrtS()/GeV,4.799,4.801))
    //     book(_h_charged, 3, 1, 2);
    //   // else if(inRange(sqrtS()/GeV,7.399,7.401))
    //     book(_h_charged, 3, 1, 3);
    }


    /// 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(PID::isCharged(p.pid())&&_h_charged&&abs(p.pid())!=13) {
	//   double x = 2.*p.p3().mod()/sqrtS();
	//   _h_charged->fill(x);
	// }
      }
      // 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() {
      // if(_h_charged) {
      // 	//scale(_h_charged, crossSection()/ sumOfWeights() /microbarn*sqr(sqrtS()));
      // }
      // R
      Scatter1D R = *_c_hadrons/ *_c_muons;
      double              rval = R.point(0).x();
      pair<double,double> rerr = R.point(0).xErrs();
      double fact = crossSection()/ sumOfWeights() /nanobarn;
      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, 1,1,1);
      Scatter2DPtr muons;
      book(muons, "sigma_muons"  );
      Scatter2DPtr mult;
      book(mult, 2,1,1);
      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   ->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 {
	  mult   ->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;
    // Histo1DPtr _h_charged;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(MARKI_1975_I100733);


}