Rivet analyses

title: BESIII_2019_I1725786

$e^+e^-\to D\bar{D}\pi^+\pi^-$ for $\sqrt{s}=4.0854$ to $4.6$ GeV

Experiment: BESIII (BEPC)

Inspire ID: 1725786

Status: VALIDATED NOHEPDATA SINGLEWEIGHT

Authors: - Peter Richardson

References: - Phys.Rev.D 100 (2019) 3, 032005

Beams: e+ e-

Beam energies: (2.0, 2.0); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3)GeV

Run details: - e+ e- to hadrons

Analysis of the resonant contributions to $e^+e^-\to D\bar{D}\pi^+\pi^-$ for $\sqrt{s}=4.0854$ to $4.6$ GeV, where $D\bar{D}=D^+D^-, D^0\bar{D}^0$. The cross sections for the production of $\pi^+\pi^-\psi(3770)$ and $D_1(2420^0\bar{D}^0$+c.c. are measured as a function of energy and the mass distrinutions are implemented for three energies.

Source code:BESIII_2019_I1725786.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- > D D pi pi class BESIII_2019_I1725786 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1725786);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(FinalState(), "FS");
  // histograms
  for (double eVal : allowedEnergies()) {

    const string en = toString(round(10 * eVal / MeV));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;

    if (en == "44156"s) {
      book(_h["Dpi0"], 1, 1, 1);
      book(_h["Dpi1"], 1, 1, 2);
      book(_h[en + "DD"], 2, 1, 3);
      book(_h[en + "mass0"], 3, 2, 1);
      book(_h[en + "mass1"], 3, 2, 2);
      book(_h[en + "mass2"], 3, 2, 3);
    }
    else if (en == "42580"s) {
      book(_h[en + "DD"], 2, 1, 1);
    }
    else if (en == "43583"s) {
      book(_h[en + "DD"], 2, 1, 2);
      book(_h[en + "mass0"], 3, 1, 1);
      book(_h[en + "mass1"], 3, 1, 2);
      book(_h[en + "mass2"], 3, 1, 3);
    }
    else if (en == "45995"s) {
      book(_h[en + "mass0"], 3, 3, 1);
      book(_h[en + "mass1"], 3, 3, 2);
      book(_h[en + "mass2"], 3, 3, 3);
    }
  }
  raiseBeamErrorIf(_sqs.empty());

  size_t ih = 0;
  for (size_t ix = 0; ix < 5; ++ix) {
    if (ix == 1) continue;
    book(_sigma[ix], 4 + ix, 1, 1);
    if (ix != 0 && ix != 2) continue;
    for (const string& en : _sigma[ix].binning().edges<0>()) {
      const double eval = stod(en) * GeV;
      if (isCompatibleWithSqrtS(eval)) {
        _edge[ih] = en;
        break;
      }
    }
    ++ih;
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  Particles fs = apply<FinalState>(event, "FS").particles();
  Particles DD, other;
  for (const Particle& p : fs) {
    Particle parent = p;
    while (!parent.parents().empty()) {
      parent = parent.parents()[0];
      if (parent.abspid() == PID::D0 || parent.abspid() == PID::DPLUS) break;
    }
    if (parent.abspid() != PID::D0 && parent.abspid() != PID::DPLUS) {
      other.push_back(p);
      continue;
    }
    bool found = false;
    for (const auto& D : DD) {
      // D already in list
      if (fuzzyEquals(D.mom(), parent.mom())) {
        found = true;
        break;
      }
    }
    if (!found) DD += parent;
  }
  //  d dbar + 2 other particles
  if (DD.size() != 2 || other.size() != 2) vetoEvent;
  // other particles pi+ pi-
  if (!(other[0].pid() == -other[1].pid() && other[0].abspid() == PID::PIPLUS)) vetoEvent;
  // d dbar pair
  if (DD[0].pid() != -DD[1].pid()) vetoEvent;
  if (other[0].pid() < 0) swap(other[0], other[1]);
  if (DD[0].pid() < 0) swap(DD[0], DD[1]);
  // fill the mass plots if needed
  if (_sqs == "44156"s && DD[0].pid() == 421) {
    _h["Dpi0"]->fill((DD[0].mom() + other[0].mom()).mass());
    _h["Dpi1"]->fill((DD[1].mom() + other[1].mom()).mass());
  }
  if (_sqs == "44156"s || _sqs == "42580"s || _sqs == "43583"s) {
    _h[_sqs + "DD"]->fill((DD[0].mom() + DD[1].mom()).mass());
  }
  const bool DstarP = (DD[0].pid() == 421 && DD[0].parents()[0].pid() == 413);
  const bool DstarM = (DD[1].pid() == -421 && DD[1].parents()[0].pid() == -413);
  const bool Dstar = DstarP || DstarM;
  if (_sqs == "44156"s || _sqs == "43583"s || _sqs == "45995"s) {
    if (DD[0].pid() == 421 && !Dstar) { // D0 pi+ pi- mass
      _h[_sqs + "mass0"]->fill((DD[0].mom() + other[0].mom() + other[1].mom()).mass());
    }
    if (DstarP) { // D*+ pi- mass
      _h[_sqs + "mass1"]->fill((DD[0].mom() + other[0].mom() + other[1].mom()).mass());
    }
    if (DD[0].pid() == 411) { // D+ pi+ pi- mass
      _h[_sqs + "mass2"]->fill((DD[0].mom() + other[0].mom() + other[1].mom()).mass());
    }
  }
  // now for the counters for the cross sections
  if (DD[0].parents()[0].pid() == 30443 && DD[1].parents()[0].pid() == 30443) {
    _sigma[0]->fill(_edge[0]);
  }
  else if (DD[0].pid() == 421
           && (DD[0].parents()[0].pid() == 10423 || DD[1].parents()[0].pid() == -10423)) {
    _sigma[2]->fill(_edge[1]);
  }
  else if (DD[0].pid() == 421
           && ((DstarP && DD[0].parents()[0].parents()[0].pid() == 10423)
               || (DstarM && DD[1].parents()[0].parents()[0].pid() == -10423))) {
    _sigma[3]->fill(_edge[1]);
  }
  else if (DD[0].pid() == 411
           && (DD[0].parents()[0].pid() == 10413 || DD[1].parents()[0].pid() == -10413)) {
    _sigma[4]->fill(_edge[1]);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // dists
  normalize(_h, 1.0, false);
  // cross sections
  const vector<double> brs = {0.93, 1.0, 1.0, 0.677, 1.0};
  const double fact = crossSection() / sumOfWeights() / picobarn;
  ;
  for (size_t ih = 0; ih < 5; ++ih) {
    if (ih == 1) continue;
    scale(_sigma[ih], fact / brs[ih]);
  }
}

/// @}


/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
BinnedHistoPtr<string> _sigma[5];
string _edge[2], _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2019_I1725786);

} ```