Rivet analyses

title: BESIII_2018_I1711382

$e^+e^-\to D_s^-\bar{D}^{(*)0} K^-$+c.c. at $\sqrt{s}=4.6$ GeV

Experiment: BESIII (BEPC)

Inspire ID: 1711382

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Chin.Phys.C 43 (2019) 3, 031001

Beams: e+ e-

Beam energies: (2.3, 2.3)GeV

Run details: - e+ e- > hadrons

Analysis of the resonant contributions to $e^+e^-\to D_s^-\bar{D}^{(*)0} K^-$+c.c. at 4.6 GeV by the BESIII collaboration.

Source code:BESIII_2018_I1711382.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief e+ e- -> Ds+ Dbar0(*) K- class BESIII_2018_I1711382 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1711382);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(FinalState(), "FS");
  // histograms
  for (unsigned int ix = 0; ix < 4; ++ix) {
    book(_h_sigma[ix], 1, 1, 1 + ix);
  }
  book(_h_cTheta, 2, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  Particles fs = apply<FinalState>(event, "FS").particles();
  Particles DS, D0, other;
  // first find the kaon and Ds
  for (const Particle& p : fs) {
    Particle parent = p;
    while (!parent.parents().empty()) {
      parent = parent.parents()[0];
      if (parent.abspid() == PID::DSPLUS || parent.abspid() == PID::D0) break;
    }
    if (parent.abspid() != PID::DSPLUS && parent.abspid() != PID::D0) {
      other.push_back(p);
      continue;
    }
    bool found = false;
    for (auto& D : parent.abspid() == PID::DSPLUS ? DS : D0) {
      // D already in list
      if (fuzzyEquals(D.mom(), parent.mom())) {
        found = true;
        break;
      }
    }
    if (!found) {
      (parent.abspid() == PID::DSPLUS ? DS : D0).push_back(parent);
    }
  }
  // Ds and D0, one particle and one anti particle
  if (DS.size() != 1 || D0.size() != 1 || DS[0].pid() * D0[0].pid() > 0) vetoEvent;
  int iK = DS[0].pid() > 0 ? -321 : 321;
  if (other.size() == 1 && other[0].pid() == iK) {
    _h_sigma[1]->fill("4.6"s);
    if (other[0].parents()[0].abspid() == 435 && D0[0].parents()[0].abspid() == 435) {
      _h_sigma[3]->fill("4.6"s);
      FourMomentum pDs2 = D0[0].momentum() + other[0].momentum();
      LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(pDs2.betaVec());
      Vector3 axis1 = pDs2.p3().unit();
      Vector3 axis2 = boost.transform(other[0].momentum()).p3().unit();
      _h_cTheta->fill(abs(axis1.dot(axis2)));
    }
  }
  else if (D0[0].parents()[0].abspid() == 423) {
    bool Dstar = true;
    for (const Particle& p : other) {
      if (p.parents()[0].abspid() != 423 && p.pid() != iK) {
        Dstar = false;
        break;
      }
    }
    if (Dstar) {
      _h_sigma[0]->fill("4.6"s);
      if (D0[0].parents()[0].parents()[0].abspid() == 10433) {
        _h_sigma[2]->fill("4.6"s);
      }
    }
  }
}

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

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _h_sigma[4];
Histo1DPtr _h_cTheta;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2018_I1711382);

} ```