Rivet analyses referenceSND_2014_I1275333Cross section for $e^+e^-\to\eta\gamma$ for energies between 1.07 and 2 GeVExperiment: SND (VEPP-2M) Inspire ID: 1275333 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Cross section for $e^+e^-\to\eta\gamma$ for energies between 1.07 and 2 GeV. Source code: SND_2014_I1275333.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 Cross section for e+e- > gamma eta
10 class SND_2014_I1275333 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2014_I1275333);
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 declare(FinalState(), "FS");
24 declare(UnstableParticles(), "UFS");
25 book(_numEtaGamma, "TMP/EtaGamma");
26 }
27
28 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
29 for (const Particle &child : p.children()) {
30 if(child.children().empty()) {
31 --nRes[child.pid()];
32 --ncount;
33 }
34 else
35 findChildren(child,nRes,ncount);
36 }
37 }
38
39 /// Perform the per-event analysis
40 void analyze(const Event& event) {
41
42 const FinalState& fs = apply<FinalState>(event, "FS");
43
44 map<long,int> nCount;
45 int ntotal(0);
46 for (const Particle& p : fs.particles()) {
47 nCount[p.pid()] += 1;
48 ++ntotal;
49 }
50
51 const FinalState& ufs = apply<FinalState>(event, "UFS");
52 for (const Particle& p : ufs.particles(Cuts::pid==221)) {
53 if(p.children().empty()) continue;
54 // find the eta
55 map<long,int> nRes = nCount;
56 int ncount = ntotal;
57 findChildren(p,nRes,ncount);
58 // eta gamma
59 if(ncount!=1) continue;
60 bool matched = true;
61 for(auto const & val : nRes) {
62 if(val.first==22) {
63 if(val.second !=1) {
64 matched = false;
65 break;
66 }
67 }
68 else if(val.second!=0) {
69 matched = false;
70 break;
71 }
72 }
73 if(matched)
74 _numEtaGamma->fill();
75 }
76 }
77
78
79 /// Normalise histograms etc., after the run
80 void finalize() {
81
82 double sigma = _numEtaGamma->val();
83 double error = _numEtaGamma->err();
84 sigma *= crossSection()/ sumOfWeights() /picobarn;
85 error *= crossSection()/ sumOfWeights() /picobarn;
86 Estimate1DPtr mult;
87 book(mult, 1, 1, 1);
88 for (auto& b : mult->bins()) {
89 if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
90 b.set(sigma, error);
91 }
92 }
93 }
94
95 /// @}
96
97
98 /// @name Histograms
99 /// @{
100 CounterPtr _numEtaGamma;
101 /// @}
102
103
104 };
105
106
107 RIVET_DECLARE_PLUGIN(SND_2014_I1275333);
108
109
110}
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