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SND_2001_I579319

Cross section for $e^+e^-2\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$ between 1 and 1.4 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 579319
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • INP-2001-34 (2001)
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$ between 1 and 1.4 GeV

Source code: SND_2001_I579319.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 SND_2001_I579319 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(SND_2001_I579319);


    /// @name Analysis methods
    //@{

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

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

      // Book histograms
      book(_npion1, "TMP/pion1");
      book(_npion2, "TMP/pion2");
    }


    /// 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]==2&&nCount[211]==2)
	_npion1->fill();
      else if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==2)
	_npion2->fill();
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=1;ix<3;++ix) {
	double sigma,error;
	if(ix==1) {
	  sigma = _npion1->val();
	  error = _npion1->err();
	}
	else {
	  sigma = _npion2->val();
	  error = _npion2->err();
	}
	sigma *= crossSection()/ sumOfWeights() /nanobarn;
	error *= crossSection()/ sumOfWeights() /nanobarn; 
	Scatter2D temphisto(refData(ix, 1, 1));
	Scatter2DPtr mult;
	book(mult, 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->addPoint(x, sigma, ex, make_pair(error,error));
	  }
	  else {
	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
	  }
	}
      }	
    }

    //@}


    /// @name Histograms
    //@{
    CounterPtr _npion1,_npion2;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(SND_2001_I579319);


}