Rivet analyses

title: BELLE_2008_I757220

Cross section for $e^+e^-\to D^+D^-$ and $D^0\bar{D}^0$ below 5 GeV

Experiment: BELLE (KEKB)

Inspire ID: 757220

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys. Rev. D77, 011103 (2008)

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Cross section for $e^+e^-\to D^+D^-$ and $D^0\bar{D}^0$ below 5 GeV

Source code:BELLE_2008_I757220.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- -> D Dbar0 class BELLE_2008_I757220 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I757220);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  book(_nD0, "/TMP/nD0");
  book(_nDp, "/TMP/nDp");
}

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 (unsigned int ix = 0; ix < ufs.particles().size(); ++ix) {
    const Particle& p1 = ufs.particles()[ix];
    if (abs(p1.pid()) != 411 && abs(p1.pid()) != 421) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1, nRes, ncount);
    bool matched = false;
    for (unsigned int iy = 0; iy < ufs.particles().size(); ++iy) {
      if (ix == iy) continue;
      const Particle& p2 = ufs.particles()[iy];
      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) {
      if (abs(p1.pid()) == 411)
        _nDp->fill();
      else if (abs(p1.pid()) == 421)
        _nD0->fill();
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 1; ix < 3; ++ix) {
    double sigma, error;
    if (ix == 1) {
      sigma = _nD0->val();
      error = _nD0->err();
    }
    else {
      sigma = _nDp->val();
      error = _nDp->err();
    }
    sigma *= crossSection() / sumOfWeights() / nanobarn;
    error *= crossSection() / sumOfWeights() / nanobarn;
    Estimate1DPtr mult;
    book(mult, ix, 1, 1);
    for (auto& b : mult->bins()) {
      if (inRange(sqrtS() / GeV, b.xMin(), b.xMax())) {
        b.set(sigma, error);
      }
    }
  }
}

/// @}


/// @name Histograms
/// @{
CounterPtr _nD0, _nDp;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2008_I757220);

} ```