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BESIII_2015_I1382146

$e^+e^-\to (D^*\bar{D}^*)^0\pi^0$ for $\sqrt{s}=4.23$ and 4.26 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1382146
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 115 (2015) 18, 182002
Beams: e+ e-
Beam energies: (2.1, 2.1); (2.1, 2.1) GeV
Run details:
  • e+ e- to hadrons, pi0 set stable

Measurement of mass distributions for $e^+e^-\to (D^*\bar{D}^*)^0\pi^0$ for $\sqrt{s}=4.23$ and 4.26 GeV by BES. The cross section for $e^+e^-\to Z_c(4025)^0\pi^0\to (D^*\bar{D}^*)^0\pi^0$ is also measured. As there is no PDG code for the $Z_c(4025)^0$ we take it to be the first unused exotic $c\bar{c}$ value 9030443, although this can be changed using the PID option.

Source code: BESIII_2015_I1382146.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief e+e- -> → D* D* pi0
 10  class BESIII_2015_I1382146 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2015_I1382146);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // set the PDG code
 23      _pid = getOption<double>("PID", 9030443);
 24      // projections
 25      declare(FinalState(), "FS");
 26      // histograms
 27      // histograms
 28      if (isCompatibleWithSqrtS(4.23)) {
 29        _ecms="4.23";
 30        book(_h[0],2,1,2);
 31      }
 32      else if (isCompatibleWithSqrtS(4.26)) {
 33        _ecms="4.26";
 34        book(_h[0],2,1,3);
 35      }
 36      else {
 37        MSG_ERROR("Beam energy incompatible with analysis.");
 38      }
 39      book(_h[1],2,1,1);
 40      book(_sigma,1,1,1);
 41    }
 42
 43
 44    /// Perform the per-event analysis
 45    void analyze(const Event& event) {
 46      Particles fs = apply<FinalState>(event, "FS").particles();
 47      Particles DD,other;
 48      for (const Particle & p : fs) {
 49        Particle parent=p;
 50        while (!parent.parents().empty()) {
 51          parent=parent.parents()[0];
 52          if(parent.abspid()==413 || parent.abspid()==423) break;
 53        }
 54        if (parent.abspid()==413 || parent.abspid()==423) {
 55          bool found=false;
 56          for (const auto& D : DD) {
 57            // D already in list
 58            if (fuzzyEquals(D.mom(), parent.mom())) {
 59              found=true;
 60              break;
 61            }
 62          }
 63          if (!found) DD.push_back(parent);
 64        }
 65        else {
 66          other.push_back(p);
 67        }
 68      }
 69      // D Dbar + neutral pion
 70      if (DD.size()!=2 || other.size()!=1) vetoEvent;
 71      if (DD[0].pid()!=-DD[1].pid()) vetoEvent;
 72      if (other[0].pid()!=111) vetoEvent;
 73      const double mass = (DD[0].momentum()+DD[1].momentum()).mass();
 74      _h[0]->fill(mass/GeV);
 75      _h[1]->fill(mass/GeV);
 76      // parent Z0
 77      if (DD[0].parents()[0].pid()==_pid && DD[1].parents()[0].pid()==_pid &&
 78          fuzzyEquals(DD[0].parents()[0].momentum(),DD[1].parents()[0].momentum()) ) _sigma->fill(_ecms);
 79    }
 80
 81
 82    /// Normalise histograms etc., after the run
 83    void finalize() {
 84      // distributions
 85      normalize(_h, 1.0, false);
 86      // cross section
 87      scale(_sigma, crossSection()/ sumOfWeights() /picobarn);
 88    }
 89    /// @}
 90
 91
 92    /// @name Histograms
 93    /// @{
 94    BinnedHistoPtr<string> _sigma;
 95    Histo1DPtr _h[2];
 96    int _pid;
 97    string _ecms;
 98    /// @}
 99
100
101  };
102
103
104  RIVET_DECLARE_PLUGIN(BESIII_2015_I1382146);
105
106}