Rivet analyses referenceKLOE_2009_I818106Mass spectrum of $\eta\pi$ in $\phi\to\eta\pi^0\gamma$ decaysExperiment: KLOE (DAPHNE) Inspire ID: 818106 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Mass spectra for $\eta\pi$ in $\phi$ decays to $\eta\pi^0\gamma$ measured by KLOE. Useful for teting the treatment of the a_0(980) meson. Source code: KLOE_2009_I818106.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief phi -> eta pi0 gamma
9 class KLOE_2009_I818106 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(KLOE_2009_I818106);
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_etapi, 1, 1, 1);
23 book(_nPhi, "TMP/PhiCounter");
24 }
25
26 void findDecayProducts(const Particle & mother, unsigned int & nstable,
27 unsigned int & neta, 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::ETA ) {
32 ++neta;
33 ++nstable;
34 ptot += p.momentum();
35 }
36 else if (id == PID::PI0) {
37 ++npi;
38 ++nstable;
39 ptot += p.momentum();
40 }
41 else if (id == PID::GAMMA) {
42 ++ngamma;
43 ++nstable;
44 }
45 else if (id == PID::PIPLUS || id == PID::PIMINUS) {
46 ++nstable;
47 }
48 else if ( !p.children().empty() ) {
49 findDecayProducts(p, nstable, neta, npi, ngamma, ptot);
50 }
51 else
52 ++nstable;
53 }
54 }
55
56 /// Perform the per-event analysis
57 void analyze(const Event& event) {
58
59 // Loop over phis
60 for(const Particle& phi : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==PID::PHI)) {
61 _nPhi->fill();
62 unsigned int nstable(0),neta(0),npi(0),ngamma(0);
63 FourMomentum p_tot(0,0,0,0);
64 findDecayProducts(phi, nstable, neta, npi, ngamma, p_tot);
65 if(nstable!=3) continue;
66 if(neta==1 && npi==1 && ngamma==1 ) {
67 _h_etapi->fill(p_tot.mass()/MeV);
68 }
69 }
70
71 }
72
73
74 /// Normalise histograms etc., after the run
75 void finalize() {
76 // normalise to total no of phi mesons
77 // and mult by 10^7 due normalisation in paper
78 scale( _h_etapi, 1./_nPhi->sumW()*1e7);
79 }
80
81 /// @}
82
83
84 /// @name Histograms
85 /// @{
86 Histo1DPtr _h_etapi;
87 CounterPtr _nPhi;
88 /// @}
89
90
91 };
92
93
94 RIVET_DECLARE_PLUGIN(KLOE_2009_I818106);
95
96
97}
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