Rivet analyses

title: BESII_2000_I505323

Measurement of $R$ for energies between 2.6 and 5 GeV

Experiment: BESII (BEPC)

Inspire ID: 505323

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 84 (2000) 594-597, 2000

Beams: e- e+

Beam energies: (1.3, 1.3); (1.6, 1.6); (1.7, 1.7); (1.8, 1.8); (2.3, 2.3); (2.5, 2.5)GeV

Run details: - e+ e- to hadrons and e+ e- to mu+ mu- (for normalization)

Measurement of $R$ in $e^+e^-$ collisions by BESII for energies between 2.6 and 5 GeV. The individual hadronic and muonic cross sections are also outputted to the yoda file so that ratio $R$ can be recalculated if runs are combined.

Source code:BESII_2000_I505323.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Measurement of R for energies between 2.6 and 5 GeV class BESII_2000_I505323 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2000_I505323);


/// @name Analysis methods
/// @{

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

  // Book histograms
  const YODA::BinnedEstimate<string>& ref = refData<YODA::BinnedEstimate<string>>(1, 1, 1);
  book(_c_hadrons, "/TMP/sigma_hadrons", ref);
  book(_c_muons, "/TMP/sigma_muons", ref);
  for (const string& en : _c_hadrons.binning().edges<0>()) {
    double eval = std::stod(en) * GeV;
    if (isCompatibleWithSqrtS(eval)) {
      _sqs = en;
      break;
    }
  }
  raiseBeamErrorIf(_sqs.empty());
}


/// 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 && nCount[13] == 1 && ntotal == 2 + nCount[22])
    _c_muons->fill(_sqs);
  else { // everything else
    _c_hadrons->fill(_sqs);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  BinnedEstimatePtr<string> mult;
  book(mult, 1, 1, 1);
  divide(_c_hadrons, _c_muons, mult);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _c_hadrons, _c_muons;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESII_2000_I505323);

} ```