Rivet analyses referenceSND_2000_I527094Mass spectrum of $\pi^0\pi^0$ in $\phi\to\pi^0\pi^0\gamma$ decaysExperiment: SND (VEPP-2M) Inspire ID: 527094 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Mass spectra for $\pi^0\pi^0$ in $\phi$ decays to $\pi^0\pi^0\gamma$ measured by SND. Source code: SND_2000_I527094.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief phi -> pi0 pi0 gamma
9 class SND_2000_I527094 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2000_I527094);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21 declare(UnstableParticles(), "UFS");
22 book(_h_pipi, 1, 1, 1);
23 book(_nPhi,"TMP/nPhi");
24 }
25
26 void findDecayProducts(const Particle & mother, unsigned int & nstable,
27 unsigned int & npi,
28 unsigned int & ngamma, FourMomentum & ptot) {
29 for(const Particle & p : mother.children()) {
30 int id = p.pid();
31 if (id == PID::PI0) {
32 ++npi;
33 ++nstable;
34 ptot += p.momentum();
35 }
36 else if (id == PID::GAMMA) {
37 ++ngamma;
38 ++nstable;
39 }
40 else if (id == PID::PIPLUS || id == PID::PIMINUS) {
41 ++nstable;
42 }
43 else if ( !p.children().empty() ) {
44 findDecayProducts(p, nstable, npi, ngamma, ptot);
45 }
46 else
47 ++nstable;
48 }
49 }
50
51 /// Perform the per-event analysis
52 void analyze(const Event& event) {
53 // Loop over phis
54 for(const Particle& phi : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==PID::PHI)) {
55 _nPhi->fill();
56 unsigned int nstable(0),npi(0),ngamma(0);
57 FourMomentum p_tot(0,0,0,0);
58 findDecayProducts(phi, nstable, npi, ngamma, p_tot);
59 if(nstable!=3) continue;
60 if(npi==2 && ngamma==1 ) {
61 _h_pipi->fill(p_tot.mass()/MeV);
62 }
63 }
64 }
65
66
67 /// Normalise histograms etc., after the run
68 void finalize() {
69 scale( _h_pipi, 1./ *_nPhi);
70 }
71
72 /// @}
73
74
75 /// @name Histograms
76 /// @{
77 Histo1DPtr _h_pipi;
78 CounterPtr _nPhi;
79 /// @}
80
81
82 };
83
84
85 RIVET_DECLARE_PLUGIN(SND_2000_I527094);
86
87
88}
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