Rivet analyses

e⁺e⁻ → (D^D̄^)^±π^∓ for $\sqrt{s}=4.26$ GeV

Experiment: BESIII (BEPC)

Inspire ID: 1247675

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 112 (2014) 13, 132001

Beams: e+ e-

Beam energies: (2.1, 2.1)GeV

Run details: - e+ e- to hadrons, pi0 set stable

Measurement of mass distributions for e⁺e⁻ → (D^*D̄^*)^±π^∓ for $\sqrt{s}=4.26$ GeV by BES. The cross section for e⁺e⁻ → Z_c(4025)^±π^∓ → (D^*D̄^*)^±π^∓ is also measured. As there is no PDG code for the $Z_c(4025)^+ we take it to be 9044213, although this can be changed using the PID option.

Source code:`BESIII_2013_I1247675.cc`

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

namespace Rivet {


  /// @brief e+e-> Z(4025)+- pi-+
  class BESIII_2013_I1247675 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1247675);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // set the PDG code
      _pid = getOption<double>("PID", 9044213);
      // projections
      declare(FinalState(), "FS");
      // histograms
      book(_sigma, 1, 1, 1);
      book(_h, 2, 1, 1);
    }


    /// 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() == 413 || parent.abspid() == 423) break;
        }
        if (parent.abspid() == 413 || parent.abspid() == 423) {
          bool found = false;
          for (const auto& D : DD) {
            // D already in list
            if (fuzzyEquals(D.momentum(), parent.momentum())) {
              found = true;
              break;
            }
          }
          if (!found) DD.push_back(parent);
        }
        else {
          other.push_back(p);
        }
      }
      // D Dbar + charged pion
      if (DD.size() != 2 || other.size() != 1) vetoEvent;
      if (DD[0].pid() * DD[1].pid() > 0) vetoEvent;
      if (other[0].abspid() != 211) vetoEvent;
      if ((DD[0].pid() == -413 && DD[1].pid() == 423 && other[0].pid() == 211)
          || (DD[0].pid() == 413 && DD[1].pid() == -423 && other[0].pid() == -211)
          || (DD[0].pid() == 423 && DD[1].pid() == -413 && other[0].pid() == 211)
          || (DD[0].pid() == -423 && DD[1].pid() == 413 && other[0].pid() == -211)) {
        const double mass = (DD[0].momentum() + DD[1].momentum()).mass();
        _h->fill(mass);
        // parent Z+/-
        if (DD[0].parents()[0].abspid() == _pid && DD[1].parents()[0].abspid() == _pid
            && fuzzyEquals(DD[0].parents()[0].mom(), DD[1].parents()[0].mom())) {
          _sigma->fill("4.26"s);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_sigma, crossSection() / sumOfWeights() / picobarn);
      normalize(_h, 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma;
    Histo1DPtr _h;
    int _pid;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2013_I1247675);

}

Rivet analyses

e+e− → (D*D̄*)±π∓ for $\sqrt{s}=4.26$ GeV

Source code:BESIII_2013_I1247675.cc

e⁺e⁻ → (D^D̄^)^±π^∓ for $\sqrt{s}=4.26$ GeV

Source code:`BESIII_2013_I1247675.cc`