Rivet analyses

title: CLEOC_2007_I761696

Cross section for $D\bar{D}$ production near the $\psi(3770)$ resonance

Experiment: CLEOC (CESR)

Inspire ID: 761696

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 76 (2007) 112001

Beams: e+ e-

Beam energies: (1.9, 1.9)GeV

Run details: - e+e- > hadrons

Measurement of the cross section for $D\bar{D}$ production near the $\psi(3770)$ resonance by CLEO-c.

Source code:CLEOC_2007_I761696.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- > D Dbar class CLEOC_2007_I761696 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2007_I761696);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(Cuts::abspid == 411 || Cuts::abspid == 421), "UFS");
  // histograms
  for (unsigned int ix = 0; ix < 3; ++ix) {
    book(_h[ix], 1, 1, 1 + ix);
  }
}

void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) {
  for (const Particle& child : p.children()) {
    if (child.children().empty()) {
      nRes[child.pid()] -= 1;
      --ncount;
    }
    else {
      findChildren(child, nRes, ncount);
    }
  }
}

/// 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;
  }
  const FinalState& ufs = apply<FinalState>(event, "UFS");
  for (const Particle& p1 : ufs.particles()) {
    if (p1.pid() < 0) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1, nRes, ncount);
    bool matched = false;
    for (const Particle& p2 : ufs.particles()) {
      if (p2.pid() != -p1.pid()) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(p2, nRes2, ncount2);
      if (ncount2 != 0) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) break;
    }
    if (matched) {
      _h[2]->fill(round(sqrtS() / MeV));
      if (p1.abspid() == 421)
        _h[0]->fill(round(sqrtS() / MeV));
      else if (p1.abspid() == 411)
        _h[1]->fill(round(sqrtS() / MeV));
      break;
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h, crossSection() / sumOfWeights() / nanobarn);
  BinnedEstimatePtr<int> ratio;
  book(ratio, 1, 1, 4);
  divide(_h[1], _h[0], ratio);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<int> _h[3];
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOC_2007_I761696);

} ```