Rivet analyses

Cross section for e⁺e⁻ → π⁺π⁻D⁺D⁻ between 4.19 and 4.946 GeV

Experiment: BESIII (BEPC)

Inspire ID: 2129305

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2208.00099

Beams: e+ e-

Beam energies: (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (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); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.5, 2.5); (2.5, 2.5); (2.5, 2.5)GeV

Run details: - e+e- to hadrons, KS0 and pi0 should be set stable

Cross section for e⁺e⁻ → π⁺π⁻D⁺D⁻ between 4.19 and 4.946 GeV. The cross section for the ψ₃(3842) resonant contribution is also measured.

Source code:`BESIII_2022_I2129305.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief e+e- > pi+pi- D+ D-
  class BESIII_2022_I2129305 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2129305);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      for (size_t ix = 0; ix < 2; ++ix) {
        book(_sigma[ix], ix + 1, 1, 1);
        for (const string& en : _sigma[ix].binning().edges<0>()) {
          const double eval = stod(en) * GeV;
          if (isCompatibleWithSqrtS(eval)) {
            _sqs[ix] = en;
            break;
          }
        }
      }
      raiseBeamErrorIf(_sqs[0].empty() && _sqs[1].empty());
    }

    void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) const {
      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");
      bool matched = false;
      for (const Particle& Dp : ufs.particles(Cuts::pid == PID::DPLUS)) {
        if (Dp.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(Dp, nRes, ncount);
        for (const Particle& Dm : ufs.particles(Cuts::pid == PID::DMINUS)) {
          if (Dm.children().empty()) continue;
          map<long, int> nRes2 = nRes;
          int ncount2 = ncount;
          findChildren(Dm, nRes2, ncount2);
          if (ncount2 != 2) continue;
          matched = true;
          for (const auto& val : nRes2) {
            if (abs(val.first) == 211) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _sigma[0]->fill(_sqs[0]);
            if (!Dm.parents().empty() && !Dp.parents().empty()) {
              // see if D+ from psi3
              Particle parent1 = Dp;
              while (!parent1.parents().empty()) {
                parent1 = parent1.parents()[0];
                if (parent1.pid() == 447) break;
              }
              if (parent1.pid() != 447) break;
              // see if D- from psi3
              Particle parent2 = Dm;
              while (!parent2.parents().empty()) {
                parent2 = parent2.parents()[0];
                if (parent2.pid() == 447) break;
              }
              if (parent2.pid() != 447) break;
              if (fuzzyEquals(parent1.momentum(), parent2.momentum())) {
                _sigma[1]->fill(_sqs[1]);
              }
            }
            break;
          }
        }
        if (matched) break;
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma[2];
    string _sqs[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2022_I2129305);

}

Rivet analyses

Cross section for e+e− → π+π−D+D− between 4.19 and 4.946 GeV

Source code:BESIII_2022_I2129305.cc

Cross section for e⁺e⁻ → π⁺π⁻D⁺D⁻ between 4.19 and 4.946 GeV

Source code:`BESIII_2022_I2129305.cc`