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## Rivet analyses reference

### BESIII_2020_I1800404

Charged particle multiplicity distributions in $J/\psi$ and $\chi_{c0,1,2}$ decays
Experiment: BESIII (BEPC)
Inspire ID: 1800404
Status: VALIDATED
Authors:
• Peter Richardson
References:
Beams: * *
Beam energies: ANY
Run details:
• Any process producing J/Psi, and chi_{0,1,2}c, originally e+e-

Measurement of the charged particle multiplicity distributions in $J/\psi$ and $\chi_{c0,1,2}$ decays by the BES collaboration.

Source code: BESIII_2020_I1800404.cc
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/UnstableParticles.hh" namespace Rivet { /// @brief J/Psi chi_c charged particle multiplicities class BESIII_2020_I1800404 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2020_I1800404); /// @name Analysis methods ///@{ /// Book histograms and initialise projections before the run void init() { // Initialise and register projections declare(UnstableParticles(Cuts::pid==443 or Cuts::pid==445 or Cuts::pid==10441 or Cuts::pid==20443),"UFS"); // histograms book(_h_chi0,1,1,1); book(_h_chi1,1,1,2); book(_h_chi2,1,1,3); book(_h_jpsi[0],2,1,1); book(_h_jpsi[1],2,1,2); } void findChildren(const Particle & p, int & nCharged) { for( const Particle &child : p.children()) { if(child.children().empty()) { if(PID::isCharged(child.pid())) ++nCharged; } else findChildren(child,nCharged); } } /// Perform the per-event analysis void analyze(const Event& event) { // loop over particles for( const Particle & p : apply(event, "UFS").particles()) { // skip radiative modes if(p.children().size()==2) { if(p.children()[0].pid()==PID::GAMMA) { if(p.children()[1].pid()==PID::GAMMA || p.children()[1].pid()==PID::JPSI) continue; } if(p.children()[1].pid()==PID::GAMMA) { if(p.children()[0].pid()==PID::GAMMA || p.children()[0].pid()==PID::JPSI) continue; } } // get the charged particle multiplicity int nCharged(0); findChildren(p,nCharged); if(p.pid()==PID::JPSI) { _h_jpsi[0]->fill(nCharged); _h_jpsi[1]->fill(nCharged); } else if(p.pid()==10441) _h_chi0->fill(nCharged); else if(p.pid()==20443) _h_chi1->fill(nCharged); else if(p.pid()==445) _h_chi2->fill(nCharged); } } /// Normalise histograms etc., after the run void finalize() { // percentage and bin width normalize(_h_jpsi[0],200.); normalize(_h_jpsi[1],200.); normalize(_h_chi0 ,200.); normalize(_h_chi1 ,200.); normalize(_h_chi2 ,200.); } ///@} /// @name Histograms ///@{ Histo1DPtr _h_jpsi[2],_h_chi0,_h_chi1,_h_chi2; ///@} }; DECLARE_RIVET_PLUGIN(BESIII_2020_I1800404); }