Rivet analyses referenceBESIII_2023_I2633025Kinematic distributions in $\eta\to\pi^+\pi^-\pi^0$ and $3\pi^0$ decaysExperiment: BESIII (BEPC) Inspire ID: 2633025 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Kinematic distributions in $\eta\to\pi^+\pi^-\pi^0$ and $3\pi^0$ decays. The data were read from the plots in the paper Source code: BESIII_2023_I2633025.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 eta -> 3 pions
10 class BESIII_2023_I2633025 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2633025);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // Initialise and register projections
23 UnstableParticles ufs = UnstableParticles(Cuts::pid==PID::ETA);
24 declare(ufs, "UFS");
25 DecayedParticles ETA(ufs);
26 ETA.addStable(PID::PI0);
27 ETA.addStable(PID::K0S);
28 declare(ETA, "ETA");
29 vector<double> bins = {-1.,-0.9,-0.8,-0.7,-0.6,-0.5,-0.4,-0.3,-0.2,-0.1,
30 0. , 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9};
31 // histograms
32 for (unsigned int ix=0; ix<2; ++ix) {
33 book(_d[ix],bins);
34 book(_c[ix],"TMP/c_"+toString(ix));
35 for(unsigned int iy=0;iy<19;++iy) {
36 book(_d[ix]->bin(iy+1),3+ix,1,1+iy);
37 }
38 }
39 }
40
41
42 /// Perform the per-event analysis
43 void analyze(const Event& event) {
44 DecayedParticles ETA = apply<DecayedParticles>(event, "ETA");
45 // loop over particles
46 for (unsigned int ix=0; ix<ETA.decaying().size(); ++ix) {
47 if (ETA.modeMatches(ix,3,mode1)) {
48 const Particle& pi0 = ETA.decayProducts()[ix].at( 111)[0];
49 const Particle& pip = ETA.decayProducts()[ix].at( 211)[0];
50 const Particle& pim = ETA.decayProducts()[ix].at(-211)[0];
51 double s1 = (pi0.mom()+pim.mom()).mass2();
52 double s2 = (pi0.mom()+pip.mom()).mass2();
53 double s3 = (pip.mom()+pim.mom()).mass2();
54 double mOut = pi0.mass()+pip.mass()+pim.mass();
55 double Q = ETA.decaying()[ix].mass()-mOut;
56 double X = sqrt(3.)/2./ETA.decaying()[ix].mass()/Q*(s1-s2);
57 double Y = 3.*(sqr(ETA.decaying()[ix].mass()-pi0.mass())-s3)/2./ETA.decaying()[ix].mass()/Q-1.;
58 _d[0]->fill(Y,X);
59 _c[0]->fill();
60 }
61 else if (ETA.modeMatches(ix,3,mode2)) {
62 const Particles& pi0 = ETA.decayProducts()[ix].at(111);
63 double s1 = (pi0[2].mom()+pi0[1].mom()).mass2();
64 double s2 = (pi0[2].mom()+pi0[0].mom()).mass2();
65 double s3 = (pi0[0].mom()+pi0[1].mom()).mass2();
66 double mOut = pi0[2].mass()+pi0[0].mass()+pi0[1].mass();
67 double Q = ETA.decaying()[ix].mass()-mOut;
68 double X = sqrt(3.)/2./ETA.decaying()[ix].mass()/Q*(s1-s2);
69 double Y = 3.*(sqr(ETA.decaying()[ix].mass()-pi0[2].mass())-s3)/2./ETA.decaying()[ix].mass()/Q-1.;
70 _d[1]->fill(Y,X);
71 _c[1]->fill();
72 }
73 }
74 }
75
76
77 /// Normalise histograms etc., after the run
78 void finalize() {
79 for(unsigned int ix=0;ix<2;++ix) {
80 scale(_d[ix],1./ *_c[ix]);
81 divByGroupWidth(_d[ix]);
82 }
83 }
84
85 /// @}
86
87
88 /// @name Histograms
89 /// @{
90 Histo1DGroupPtr _d[2];
91 CounterPtr _c[2];
92 const map<PdgId,unsigned int> mode1 = { {211,1}, {-211,1}, {111,1} };
93 const map<PdgId,unsigned int> mode2 = { {111,3} };
94 /// @}
95
96
97 };
98
99
100 RIVET_DECLARE_PLUGIN(BESIII_2023_I2633025);
101
102}
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