Rivet analyses

title: BABAR_2009_I815035

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

Experiment: BABAR (PEP-II)

Inspire ID: 815035

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D79 (2009) 092001

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to D^{0}\bar{D}^{0}$, $D^{+}\bar{D}^{-}$ and $D^{}\bar{D}^{}$ by the BaBar collaboration.

Source code:BABAR_2009_I815035.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D D and D D* cross section class BABAR_2009_I815035 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I815035);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");

  // Book histograms
  book(_c_D0_Dstar, "/TMP/c_D0_Dstar");
  book(_c_Dplus_Dstar, "/TMP/c_Dplus_Dstar");
  book(_c_D_Dstar, "/TMP/c_D_Dstar");
  book(_c_Dstar_Dstar, "/TMP/c_Dstar_Dstar");
}


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");
  // total hadronic and muonic cross sections
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  // unstable charm analysis
  Particles ds = apply<UnstableParticles>(event, "UFS")
                     .particles(Cuts::abspid == 411 or Cuts::abspid == 413 or Cuts::abspid == 421
                                or Cuts::abspid == 423);
  for (unsigned int ix = 0; ix < ds.size(); ++ix) {
    const Particle& p1 = ds[ix];
    int id1 = abs(p1.pid());
    // check fs
    bool fs = true;
    for (const Particle& child : p1.children()) {
      if (child.pid() == p1.pid()) {
        fs = false;
        break;
      }
    }
    if (!fs) continue;
    // find the children
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1, nRes, ncount);
    bool matched = false;
    int sign = p1.pid() / id1;
    // loop over the other fs particles
    for (unsigned int iy = ix + 1; iy < ds.size(); ++iy) {
      const Particle& p2 = ds[iy];
      fs = true;
      for (const Particle& child : p2.children()) {
        if (child.pid() == p2.pid()) {
          fs = false;
          break;
        }
      }
      if (!fs) continue;
      if (p2.pid() / abs(p2.pid()) == sign) continue;
      int id2 = abs(p2.pid());
      if (!p2.parents().empty() && p2.parents()[0].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) {
        if ((id1 == 421 && id2 == 423) || (id1 == 423 && id2 == 421)) {
          _c_D0_Dstar->fill();
          _c_D_Dstar->fill();
        }
        else if ((id1 == 411 && id2 == 413) || (id1 == 413 && id2 == 411)) {
          _c_Dplus_Dstar->fill();
          _c_D_Dstar->fill();
        }
        else if ((id1 == 413 && id2 == 413) || (id1 == 423 && id2 == 423)) {
          _c_Dstar_Dstar->fill();
        }
        break;
      }
    }
    if (matched) break;
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  double fact = crossSection() / sumOfWeights() / nanobarn;
  for (unsigned int ih = 1; ih < 5; ++ih) {
    double sigma = 0.0, error = 0.0;
    unsigned int ix = 1, iy = ih;
    if (ih == 1) {
      sigma = _c_D0_Dstar->val() * fact;
      error = _c_D0_Dstar->err() * fact;
    }
    else if (ih == 2) {
      sigma = _c_Dplus_Dstar->val() * fact;
      error = _c_Dplus_Dstar->err() * fact;
    }
    else if (ih == 3) {
      sigma = _c_D_Dstar->val() * fact;
      error = _c_D_Dstar->err() * fact;
    }
    else if (ih == 4) {
      sigma = _c_Dstar_Dstar->val() * fact;
      error = _c_Dstar_Dstar->err() * fact;
      ix = 2;
      iy = 1;
    }
    Estimate1DPtr mult;
    book(mult, ix, 1, iy);
    for (auto& b : mult->bins()) {
      if (inRange(sqrtS() / GeV, b.xMin(), b.xMax())) {
        b.set(sigma, error);
      }
    }
  }
}

/// @}


/// @name Histograms
/// @{
CounterPtr _c_D0_Dstar, _c_Dplus_Dstar, _c_D_Dstar, _c_Dstar_Dstar;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2009_I815035);

} ```