Rivet analyses

title: BESII_2006_I717720

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

Experiment: BESII (BEPC)

Inspire ID: 717720

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 121801

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- > hadrons

Measurement of the cross section for $e^+e^-\to\text{hadrons}$ for $\sqrt{s}=3.65\to3.87\,$GeV. In addition the cross section to charm hadrons near the $\psi(3770)$ is measured. 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:BESII_2006_I717720.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- > hadrons class BESII_2006_I717720 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2006_I717720);


/// @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), "UFS");
  declare(FinalState(), "FS");

  // Book histograms
  book(_sigma[0], 1, 1, 1);
  for (unsigned int ix = 1; ix < 4; ++ix) book(_sigma[ix], 2, 1, ix);
  string eCent = getOption<string>("ECENT", std::to_string(sqrtS() / GeV));
  double ee = std::stod(eCent);
  for (unsigned int ix = 0; ix < 3; ++ix) {
    for (const auto& en : _sigma[ix].binning().edges<0>()) {
      if (fuzzyEquals(std::stod(en), ee, 1e-5)) {
        _ecms[ix] = en;
        break;
      }
    }
  }
  if (_ecms[0].empty() && _ecms[1].empty() && _ecms[2].empty())
    MSG_ERROR("Beam energy incompatible with analysis.");
  _ecms[3] = _ecms[2];
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  const FinalState& ufs = apply<FinalState>(event, "UFS");
  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 {
    if (!_ecms[0].empty()) _sigma[0]->fill(_ecms[0]);
    if (!ufs.particles().empty()) {
      if (!_ecms[1].empty()) _sigma[1]->fill(_ecms[1]);
      if (ufs.particles()[0].abspid() == 421) {
        if (!_ecms[2].empty()) _sigma[2]->fill(_ecms[2]);
      }
      else {
        if (!_ecms[3].empty()) _sigma[3]->fill(_ecms[3]);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  double fact = crossSection() / sumOfWeights() / nanobarn;
  for (unsigned int ix = 0; ix < 4; ++ix) scale(_sigma[ix], fact);
}

/// @}

/// @name Histograms
/// @{
BinnedHistoPtr<string> _sigma[4];
string _ecms[4];
/// @}

};

RIVET_DECLARE_PLUGIN(BESII_2006_I717720);

} ```