Rivet analyses referenceCMD2_1999_I503154Cross section for $e^+e^-\to\eta\gamma$ for energies near the $\phi$ massExperiment: (VEPP-2M) Inspire ID: 503154 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Cross section for $e^+e^-\to\eta\gamma$ for energies near the $\phi$ mass. Source code: CMD2_1999_I503154.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 Add a short analysis description here
10 class CMD2_1999_I503154 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_1999_I503154);
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, "TMP/EtaGamma");
27 }
28
29
30 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
31 for (const Particle &child : p.children()) {
32 if(child.children().empty()) {
33 --nRes[child.pid()];
34 --ncount;
35 }
36 else
37 findChildren(child,nRes,ncount);
38 }
39 }
40
41 /// Perform the per-event analysis
42 void analyze(const Event& event) {
43
44 const FinalState& fs = apply<FinalState>(event, "FS");
45
46 map<long,int> nCount;
47 int ntotal(0);
48 for (const Particle& p : fs.particles()) {
49 nCount[p.pid()] += 1;
50 ++ntotal;
51 }
52
53 const FinalState& ufs = apply<FinalState>(event, "UFS");
54 for (const Particle& p : ufs.particles()) {
55 if(p.children().empty()) continue;
56 // find the omega
57 if(p.pid()==221) {
58 map<long,int> nRes = nCount;
59 int ncount = ntotal;
60 findChildren(p,nRes,ncount);
61 // eta pi+pi-
62 if(ncount!=1) continue;
63 bool matched = true;
64 for(auto const & val : nRes) {
65 if(val.first==22) {
66 if(val.second !=1) {
67 matched = false;
68 break;
69 }
70 }
71 else if(val.second!=0) {
72 matched = false;
73 break;
74 }
75 }
76 if(matched)
77 _numEtaGamma->fill();
78 }
79 }
80
81 }
82
83
84 /// Normalise histograms etc., after the run
85 void finalize() {
86 double sigma = _numEtaGamma->val();
87 double error = _numEtaGamma->err();
88 sigma *= crossSection()/ sumOfWeights() /nanobarn;
89 error *= crossSection()/ sumOfWeights() /nanobarn;
90 Estimate1DPtr mult;
91 book(mult, 1, 1, 1);
92 for (auto& b : mult->bins()) {
93 if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
94 b.set(sigma, error);
95 }
96 }
97 }
98
99 /// @}
100
101
102 /// @name Histograms
103 /// @{
104 CounterPtr _numEtaGamma;
105 /// @}
106
107
108 };
109
110
111 RIVET_DECLARE_PLUGIN(CMD2_1999_I503154);
112
113
114}
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