Rivet analyses referenceCMD2_2001_I554522Cross section for $e^+e^-\to\eta\gamma$ for energies between 600 MeV and 1380 MeVExperiment: CMD2 (VEPP-2M) Inspire ID: 554522 Status: VALIDATED Authors:
Beam energies: (0.3, 0.3); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.4, 0.4); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.6, 0.6); (0.7, 0.7) GeV Run details:
Cross section for $e^+e^-\to\eta\gamma$ for energies between 600 MeV and 1380 MeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: CMD2_2001_I554522.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/UnstableParticles.hh"
5
6namespace Rivet {
7
8
9 /// @brief e+e- -> eta gamma
10 class CMD2_2001_I554522 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_2001_I554522);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22
23 // Initialise and register projections
24 declare(FinalState(), "FS");
25 declare(UnstableParticles(), "UFS");
26 book(_numEtaGamma, 1, 1, 1);
27 for (const string& en : _numEtaGamma.binning().edges<0>()) {
28 double end = std::stod(en)*MeV;
29 if(isCompatibleWithSqrtS(end)) {
30 _ecms = en;
31 break;
32 }
33 }
34 if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
35 }
36
37 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
38 for (const Particle &child : p.children()) {
39 if(child.children().empty()) {
40 --nRes[child.pid()];
41 --ncount;
42 }
43 else
44 findChildren(child,nRes,ncount);
45 }
46 }
47
48
49 /// Perform the per-event analysis
50 void analyze(const Event& event) {
51
52 const FinalState& fs = apply<FinalState>(event, "FS");
53
54 map<long,int> nCount;
55 int ntotal(0);
56 for (const Particle& p : fs.particles()) {
57 nCount[p.pid()] += 1;
58 ++ntotal;
59 }
60
61 const FinalState& ufs = apply<FinalState>(event, "UFS");
62 for (const Particle& p : ufs.particles()) {
63 if(p.children().empty()) continue;
64 // find the omega
65 if(p.pid()==221) {
66 map<long,int> nRes = nCount;
67 int ncount = ntotal;
68 findChildren(p,nRes,ncount);
69 // eta pi+pi-
70 if(ncount!=1) continue;
71 bool matched = true;
72 for(auto const & val : nRes) {
73 if(val.first==22) {
74 if(val.second !=1) {
75 matched = false;
76 break;
77 }
78 }
79 else if(val.second!=0) {
80 matched = false;
81 break;
82 }
83 }
84 if(matched)
85 _numEtaGamma->fill(_ecms);
86 }
87 }
88
89 }
90
91
92 /// Normalise histograms etc., after the run
93 void finalize() {
94 scale(_numEtaGamma, crossSection()/ sumOfWeights() /nanobarn);
95 }
96
97 /// @}
98
99
100 /// @name Histograms
101 /// @{
102 BinnedHistoPtr<string> _numEtaGamma;
103 string _ecms;
104 /// @}
105
106
107 };
108
109
110 RIVET_DECLARE_PLUGIN(CMD2_2001_I554522);
111
112
113}
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