Rivet analyses referenceBESII_2009_I819937$J/\psi\to p \bar{p}\pi^0$Experiment: BESII (BEPC) Inspire ID: 819937 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the mass distributions in the decay $J/\psi\to p \bar{p}\pi^0$. The data were read from the plots in the paper, but is corrected for detector efficiency. Source code: BESII_2009_I819937.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/DecayedParticles.hh"
5
6namespace Rivet {
7
8
9 /// @brief J/psi -> p pbar pi0
10 class BESII_2009_I819937 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2009_I819937);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 UnstableParticles ufs = UnstableParticles(Cuts::pid==443);
23 declare(ufs, "UFS");
24 DecayedParticles psi(ufs);
25 psi.addStable(PID::PI0);
26 psi.addStable(PID::K0S);
27 psi.addStable(PID::ETA);
28 psi.addStable(PID::ETAPRIME);
29 declare(psi, "psi");
30 for(unsigned int ix=0;ix<2;++ix)
31 book(_h[ix],1,1,1+ix);
32 book(_dalitz, "dalitz",50,1.,5.,50,1.,5.);
33 }
34
35
36 /// Perform the per-event analysis
37 void analyze(const Event& event) {
38 static const map<PdgId,unsigned int> & mode = { { 2212,1}, {-2212,1}, { 111,1} };
39 DecayedParticles psi = apply<DecayedParticles>(event, "psi");
40 // loop over particles
41 for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
42 if(!psi.modeMatches(ix,3,mode)) continue;
43 const Particles & pi0 = psi.decayProducts()[ix].at( 111);
44 const Particles & pp = psi.decayProducts()[ix].at( 2212);
45 const Particles & pbar = psi.decayProducts()[ix].at(-2212);
46 double mminus = (pbar[0].momentum()+pi0 [0].momentum()).mass2();
47 double mplus = (pp [0].momentum()+pi0 [0].momentum()).mass2();
48 _h[0]->fill(sqrt(mplus ));
49 _h[1]->fill(sqrt(mminus));
50 _dalitz->fill(mplus,mminus);
51 }
52 }
53
54
55 /// Normalise histograms etc., after the run
56 void finalize() {
57 normalize(_dalitz);
58 for(unsigned int ix=0;ix<2;++ix)
59 normalize(_h[ix]);
60 }
61
62 /// @}
63
64
65 /// @name Histograms
66 /// @{
67 Histo1DPtr _h[2];
68 Histo2DPtr _dalitz;
69 /// @}
70
71
72 };
73
74
75 RIVET_DECLARE_PLUGIN(BESII_2009_I819937);
76
77}
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