Rivet analyses referenceCMD2_2005_I658856Cross section for $e^+e^-\to\pi\gamma$ and $\eta\gamma$ for energies between 600 MeV and 1380 MeVExperiment: CMD2 (VEPP-2M) Inspire ID: 658856 Status: VALIDATED Authors:
Beam energies: (0.3, 0.3); (0.3, 0.3); (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); (0.5, 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); (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.6, 0.6); (0.7, 0.7) GeV Run details:
Cross section for $e^+e^-\to\pi\gamma$ and $\eta\gamma$ for energies between 600 MeV and 1380 MeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: CMD2_2005_I658856.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 or pi0 + gamma
10 class CMD2_2005_I658856 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_2005_I658856);
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 for(unsigned int ix=0;ix<2;++ix) {
27 book(_sigma[ix], 1+ix, 1, 1);
28 for (const string& en : _sigma[ix].binning().edges<0>()) {
29 const double end = std::stod(en)*MeV;
30 if (isCompatibleWithSqrtS(end)) {
31 _ecms[ix] = en;
32 break;
33 }
34 }
35 }
36 if (_ecms[0].empty() && _ecms[1].empty() && _ecms[2].empty()) {
37 MSG_ERROR("Beam energy incompatible with analysis.");
38 }
39 }
40
41 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
42 for (const Particle &child : p.children()) {
43 if(child.children().empty()) {
44 --nRes[child.pid()];
45 --ncount;
46 }
47 else
48 findChildren(child,nRes,ncount);
49 }
50 }
51
52 /// Perform the per-event analysis
53 void analyze(const Event& event) {
54
55 const FinalState& fs = apply<FinalState>(event, "FS");
56
57 map<long,int> nCount;
58 int ntotal(0);
59 for (const Particle& p : fs.particles()) {
60 nCount[p.pid()] += 1;
61 ++ntotal;
62 }
63 if(ntotal==2 && nCount[22]==1 && nCount[111]==1)
64 _sigma[1]->fill(_ecms[1]);
65
66
67 const FinalState& ufs = apply<FinalState>(event, "UFS");
68 for (const Particle& p : ufs.particles()) {
69 if(p.children().empty()) continue;
70 // find the omega
71 if(p.pid()==221) {
72 map<long,int> nRes = nCount;
73 int ncount = ntotal;
74 findChildren(p,nRes,ncount);
75 // eta pi+pi-
76 if(ncount!=1) continue;
77 bool matched = true;
78 for(auto const & val : nRes) {
79 if(val.first==22) {
80 if(val.second !=1) {
81 matched = false;
82 break;
83 }
84 }
85 else if(val.second!=0) {
86 matched = false;
87 break;
88 }
89 }
90 if(matched)
91 _sigma[0]->fill(_ecms[0]);
92 }
93 }
94
95 }
96
97
98 /// Normalise histograms etc., after the run
99 void finalize() {
100 double fact = crossSection()/ sumOfWeights() /nanobarn;
101 for (unsigned int ix=0;ix<2;++ix) {
102 scale(_sigma[ix],fact);
103 }
104 }
105
106 /// @}
107
108
109 /// @name Histograms
110 /// @{
111 BinnedHistoPtr<string> _sigma[2];
112 string _ecms[2];
113 /// @}
114
115
116 };
117
118
119 RIVET_DECLARE_PLUGIN(CMD2_2005_I658856);
120
121
122}
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