Rivet analyses referenceBESIII_2016_I1484158$\eta\pi^0$ mass distribution in $J/\psi\to\gamma\eta\pi^0$Experiment: BESIII (BEPC) Inspire ID: 1484158 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the $\eta\pi^0$ mass distribution in $J/\psi\to\gamma\eta\pi^0$ decays. The data were read from the plots in the paper and the backgrounds given subtracted, although acceptance/efficiency may not be corrected. Source code: BESIII_2016_I1484158.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 -> gamma eta pi0
10 class BESIII_2016_I1484158 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2016_I1484158);
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::ETA);
27 declare(psi, "psi");
28 //histograms
29 book(_h,1,1,1);
30 }
31
32
33 /// Perform the per-event analysis
34 void analyze(const Event& event) {
35 static const map<PdgId,unsigned int> & mode = { {221,1} , {111,1}, {22,1} };
36 DecayedParticles psi = apply<DecayedParticles>(event, "psi");
37 // loop over particles
38 for(unsigned int ix=0;ix<psi.decaying().size();++ix) {
39 if(!psi.modeMatches(ix,3,mode)) continue;
40 const Particle & eta = psi.decayProducts()[ix].at( 221)[0];
41 const Particle & pi0 = psi.decayProducts()[ix].at( 111)[0];
42 _h->fill((eta.momentum()+pi0.momentum()).mass());
43 }
44 }
45
46
47 /// Normalise histograms etc., after the run
48 void finalize() {
49 normalize(_h,1.,false);
50 }
51
52 /// @}
53
54
55 /// @name Histograms
56 /// @{
57 Histo1DPtr _h;
58 /// @}
59
60
61 };
62
63
64 RIVET_DECLARE_PLUGIN(BESIII_2016_I1484158);
65
66}
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