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BESIII_2014_I1286898

Cross section for $e^+e^-\to$ proton and antiproton between 3.65 and 3.9 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1286898
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B735 (2014) 101-107, 2014
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to p\bar{p}$ for energies between 3.65 and 3.9 GeV

Source code: BESIII_2014_I1286898.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 BESIII_2014_I1286898 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2014_I1286898);


    /// @name Analysis methods
    //@{

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

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

      // Book histograms
      book(_nproton, "TMP/proton");

    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      if(fs.particles().size()!=2) vetoEvent;
      for (const Particle& p : fs.particles()) {
	if(abs(p.pid())!=PID::PROTON) vetoEvent;
      }
      _nproton->fill();
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double sigma = _nproton->val();
      double error = _nproton->err();
      sigma *= crossSection()/ sumOfWeights() /picobarn;
      error *= crossSection()/ sumOfWeights() /picobarn; 
      Scatter2D temphisto(refData(1, 1, 6));
      Scatter2DPtr  mult;
      book(mult, 1, 1, 6);
      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 _nproton;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BESIII_2014_I1286898);


}