Rivet analyses

title: BELLE_2008_I759073

Cross section for $e^+e^-\to D^0D^-\pi^++\text{c.c.}$ below 5 GeV

Experiment: BELLE (KEKB)

Inspire ID: 759073

Status: VALIDATED

Authors: - Peter Richardson

References: none listed

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Cross section for $e^+e^-\to D^0D^-\pi^++\text{c.c.}$ below 5 GeV

Source code:BELLE_2008_I759073.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Cross section for D0 D- pi+ +c.c class BELLE_2008_I759073 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I759073);


/// @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");
}

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()) != 421) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1, nRes, ncount);
    bool matched = false;
    int id2 = p1.pid() > 0 ? -411 : 411;
    int ipi = p1.pid() > 0 ? 211 : -211;
    for (unsigned int iy = 0; iy < ufs.particles().size(); ++iy) {
      if (ix == iy) continue;
      const Particle& p2 = ufs.particles()[iy];
      if (p2.pid() != id2) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(p2, nRes2, ncount2);
      if (ncount2 != 1) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.first == ipi) {
          if (val.second != 1) {
            matched = false;
            break;
          }
        }
        else if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) break;
    }
    if (matched) _nD0->fill();
  }
}


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

/// @}

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

};

RIVET_DECLARE_PLUGIN(BELLE_2008_I759073);

} ```