Rivet analyses

title: BESII_2008_I801210

Cross-sections for light hadrons at 3.773, 3.650 and 3.6648 GeV

Experiment: BESII (BEPC II)

Inspire ID: 801210

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B670 (2008) 184-189, 2008

Beams: e+ e-

Beam energies: (1.9, 1.9); (1.8, 1.8); (1.8, 1.8)GeV

Run details: - e+e- to hadrons

Cross section for $e^+e^-\to \pi^+\pi^-$, $K^+K^-$, $2\pi^+2\pi^-$, $K^+K^-\pi^+\pi^-$ and $3\pi^+3\pi^-$ together with a $\pi^0\pi^0$ pair at 3.773, 3.650 and 3.6648 GeV.

Source code:BESII_2008_I801210.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Cross-sections for light hadrons at 3.773, 3.650 and 3.6648 GeV class BESII_2008_I801210 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2008_I801210);


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

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

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

  // Book histograms
  for (size_t ix = 1; ix < 6; ++ix) {
    book(_nMeson[ix], 1, 1, ix);
  }
  for (const string& en : _nMeson[1].binning().edges<0>()) {
    const double eval = stod(en);
    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;
  }
  if (nCount[111] != 2) vetoEvent;

  if (ntotal == 4) {
    if (nCount[211] == 1 && nCount[-211] == 1)
      _nMeson[1]->fill(_sqs);
    else if (nCount[321] == 1 && nCount[-321] == 1)
      _nMeson[2]->fill(_sqs);
  }
  else if (ntotal == 6) {
    if (nCount[211] == 2 && nCount[-211] == 2)
      _nMeson[3]->fill(_sqs);
    else if (nCount[321] == 1 && nCount[-321] == 1 && nCount[211] == 1 && nCount[-211] == 1)
      _nMeson[4]->fill(_sqs);
  }
  else if (ntotal == 8) {
    if (nCount[211] == 3 && nCount[-211] == 3) _nMeson[5]->fill(_sqs);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_nMeson, crossSection() / sumOfWeights() / picobarn);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _nMeson[6];
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESII_2008_I801210);

} ```