Rivet analyses

title: BESIII_2008_I779017

Cross section for light hadron production for $\sqrt{s}=3.65\to3.87\,$GeV

Experiment: BESIII (BEPC)

Inspire ID: 779017

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 659 (2008) 74-79

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- > hadrons

Measurement of the cross section for $e^+e^-\to\text{light hadrons}$ for $\sqrt{s}=3.65\to3.87\,$GeV. As the analyses requires the beam energy smearing described in the paper then central CMS energy should be specified using the ECENT (in GeV) option.

Source code:BESIII_2008_I779017.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- > light hadrons class BESIII_2008_I779017 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2008_I779017);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(Cuts::abspid == 411 || Cuts::abspid == 421 || Cuts::abspid == 431
                            || Cuts::abspid == 4122 || Cuts::abspid == 4232 || Cuts::abspid == 4132
                            || Cuts::abspid == 4332),
          "UFS");
  declare(FinalState(), "FS");

  // Book histograms
  book(_sigma, 1, 1, 1);
  _eCent = getOption<string>("ECENT", std::to_string(sqrtS() / GeV));
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  const FinalState& ufs = apply<FinalState>(event, "UFS");
  if (!ufs.particles().empty()) vetoEvent;
  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 and nCount[13] == 1 && ntotal == 2 + nCount[22])
    vetoEvent;
  else if (nCount[-11] == 1 and nCount[11] == 1 && ntotal == 2 + nCount[22])
    vetoEvent;
  // everything else
  else
    _sigma->fill(_eCent);
}


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

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _sigma;
string _eCent;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2008_I779017);

} ```