Rivet analyses

Cross section for e⁺e⁻ → D⁺D⁻π⁺π⁻ for E_CMS = 4.36 → 4.60 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1756876

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 1909.12478

Beams: e- e+

Beam energies: (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

Cross section for e⁺e⁻ → D⁺D⁻π⁺π⁻ for E_CMS = 4.36 → 4.60 GeV. The cross sections for the subprocesses e⁺e⁻ → D₁(2420)^±D^∓ and e⁺e⁻ → ψ(3770)π⁺π⁻ are measured.

Source code:`BESIII_2019_I1756876.cc`

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

namespace Rivet {


  /// @brief Cross section for D+D- pi+ pi- (D1 D and psi(3770) pi+pi- subprocesses)
  class BESIII_2019_I1756876 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1756876);


    /// @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(_nD1D, 1, 1, 1);
      book(_nPsi, 1, 1, 2);
      for (const string& en : _nD1D.binning().edges<0>()) {
        const double eval = stod(en) * MeV;
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en;
          break;
        }
      }
      raiseBeamErrorIf(_sqs.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& p1 : ufs.particles(Cuts::abspid == 411)) {
        int sign = p1.pid() / 411;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p1, nRes, ncount);
        matched = false;
        for (const Particle& p2 : ufs.particles(Cuts::pid == -sign * 411)) {
          map<long, int> nRes2 = nRes;
          int ncount2 = ncount;
          findChildren(p2, 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) break;
        }
        if (matched) break;
      }
      if (!matched) vetoEvent;
      // psi(3770) pi+pi-
      for (const Particle& p1 : ufs.particles(Cuts::abspid == 30443)) {
        if (p1.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p1, nRes, ncount);
        // psi(3770) pi+pi-
        if (ncount != 2) continue;
        bool matched = true;
        for (const auto& val : nRes) {
          if (abs(val.first) == 211) {
            if (val.second != 1) {
              matched = false;
              break;
            }
          }
          else if (val.second != 0) {
            matched = false;
            break;
          }
        }
        if (matched) {
          _nPsi->fill(_sqs);
          return;
        }
      }
      // D1 D
      for (const Particle& p1 : ufs.particles(Cuts::abspid == 10413)) {
        if (p1.children().empty()) continue;
        int sign = p1.pid() / 10413;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p1, nRes, ncount);
        matched = false;
        for (const Particle& p2 : ufs.particles(Cuts::pid == -sign * 411)) {
          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) break;
        }
        if (matched) {
          _nD1D->fill(_sqs);
          return;
        }
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection() / sumOfWeights() / picobarn;
      scale(_nD1D, fact);
      scale(_nPsi, fact);
    }

    /// @}

    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _nD1D, _nPsi;
    string _sqs = "";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2019_I1756876);

}

Rivet analyses

Cross section for e+e− → D+D−π+π− for ECMS = 4.36 → 4.60 GeV

Source code:BESIII_2019_I1756876.cc

Cross section for e⁺e⁻ → D⁺D⁻π⁺π⁻ for E_CMS = 4.36 → 4.60 GeV

Source code:`BESIII_2019_I1756876.cc`