Rivet analyses

title: BELLE_2004_I643565

Cross section for $e^+e^-\to D^{()+}D^{()-}$ at $\sqrt{s}=10.58$GeV

Experiment: BELLE (KEKB)

Inspire ID: 643565

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 70 (2004) 071101

Beams: e+ e-

Beam energies: (5.3, 5.3)GeV

Run details: - e+e- > hadrons

Cross section for $e^+e^-\to D^{()+}D^{()-}$ at $\sqrt{s}=10.58$GeV

Source code:BELLE_2004_I643565.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+e- > D()+ D()- class BELLE_2004_I643565 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2004_I643565);


/// @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 == 413), "UFS");
  // histos
  book(_h_sigma[0], 1, 1, 2);
  book(_h_sigma[1], 1, 1, 5);
  book(_h_hel, 2, 1, 1);
}

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");
  Particle Dstar;
  for (unsigned int ix = 0; ix < ufs.particles().size(); ++ix) {
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(ufs.particles()[ix], nRes, ncount);
    bool matched = false;
    for (unsigned int iy = ix + 1; iy < ufs.particles().size(); ++iy) {
      if (ufs.particles()[ix].pid() * ufs.particles()[iy].pid() > 0) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(ufs.particles()[iy], nRes2, ncount2);
      if (ncount2 != 0) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        if (ufs.particles()[ix].abspid() == 413 && ufs.particles()[iy].abspid() == 413) {
          _h_sigma[0]->fill("10.58"s);
        }
        else if (ufs.particles()[ix].abspid() == 411 && ufs.particles()[iy].abspid() == 413) {
          _h_sigma[1]->fill("10.58"s);
          Dstar = ufs.particles()[iy];
        }
        else if (ufs.particles()[iy].abspid() == 411 && ufs.particles()[ix].abspid() == 413) {
          _h_sigma[1]->fill("10.58"s);
          Dstar = ufs.particles()[ix];
        }
        break;
      }
    }
    if (matched) break;
  }
  if (Dstar.abspid() == 413 && Dstar.children().size() == 2) {
    Particle pim;
    int sign = Dstar.pid() / Dstar.abspid();
    if (Dstar.children()[0].pid() == sign * 211 && Dstar.children()[1].pid() == sign * 421) {
      pim = Dstar.children()[0];
    }
    else if (Dstar.children()[1].pid() == sign * 211 && Dstar.children()[0].pid() == sign * 421) {
      pim = Dstar.children()[1];
    }
    else {
      return;
    }
    const LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(Dstar.mom().betaVec());
    FourMomentum pPim = boost2.transform(pim.mom());
    _h_hel->fill(pPim.p3().unit().dot(Dstar.mom().p3().unit()));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_sigma, crossSection() / picobarn / sumOfWeights());
  normalize(_h_hel, 1.0, false);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _h_sigma[2];
Histo1DPtr _h_hel;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2004_I643565);

} ```