Rivet analyses referenceBESIII_2021_I1940960Measurement of cross section for $e^+e^-\to\Sigma^0\bar{\Sigma}^0$ between 2.3864 and 3.02 GeVExperiment: BESIII (BEPC) Inspire ID: 1940960 Status: VALIDATED Authors:
Beam energies: (1.2, 1.2); (1.2, 1.2); (1.2, 1.2); (1.3, 1.3); (1.3, 1.3); (1.4, 1.4); (1.5, 1.5) GeV Run details:
Measurement of the cross section for $e^+e^-\to\Sigma^0\bar{\Sigma}^0$ between 2.3864 and 3.02 GeV by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2021_I1940960.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 Sigma0 SigmaBar0 cross section
10 class BESIII_2021_I1940960 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1940960);
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(_nSigma, 1, 1, 1);
26 for (const string& en : _nSigma.binning().edges<0>()) {
27 const double end = std::stod(en)*GeV;
28 if (isCompatibleWithSqrtS(end)) {
29 _ecms = en;
30 break;
31 }
32 }
33 if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
34 }
35
36 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
37 for(const Particle &child : p.children()) {
38 if(child.children().empty()) {
39 nRes[child.pid()]-=1;
40 --ncount;
41 }
42 else
43 findChildren(child,nRes,ncount);
44 }
45 }
46
47 /// Perform the per-event analysis
48 void analyze(const Event& event) {
49 const FinalState& fs = apply<FinalState>(event, "FS");
50 // total hadronic and muonic cross sections
51 map<long,int> nCount;
52 int ntotal(0);
53 for (const Particle& p : fs.particles()) {
54 nCount[p.pid()] += 1;
55 ++ntotal;
56 }
57 // find the Xis
58 const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
59 for(const Particle & p1 : ufs.particles(Cuts::pid==3212)) {
60 bool matched = false;
61 // check fs
62 bool fs = true;
63 for(const Particle & child : p1.children()) {
64 if(child.pid()==p1.pid()) {
65 fs = false;
66 break;
67 }
68 }
69 if(!fs) continue;
70 // find the children
71 map<long,int> nRes = nCount;
72 int ncount = ntotal;
73 findChildren(p1,nRes,ncount);
74 for(const Particle & p2 : ufs.particles(Cuts::pid==-3212)) {
75 // check fs
76 bool fs = true;
77 for(const Particle & child : p2.children()) {
78 if(child.pid()==p2.pid()) {
79 fs = false;
80 break;
81 }
82 }
83 if(!fs) continue;
84 map<long,int> nRes2 = nRes;
85 int ncount2 = ncount;
86 findChildren(p2,nRes2,ncount2);
87 if(ncount2!=0) continue;
88 matched=true;
89 for(auto const & val : nRes2) {
90 if(val.second!=0) {
91 matched = false;
92 break;
93 }
94 }
95 if(matched) {
96 _nSigma->fill(_ecms);
97 break;
98 }
99 }
100 if(matched) break;
101 }
102 }
103
104
105 /// Normalise histograms etc., after the run
106 void finalize() {
107 scale(_nSigma, crossSection()/ sumOfWeights() /picobarn);
108 }
109
110 ///@}
111
112
113 /// @name Histograms
114 ///@{
115 BinnedHistoPtr<string> _nSigma;
116 ///@}
117 string _ecms;
118
119
120 };
121
122
123 RIVET_DECLARE_PLUGIN(BESIII_2021_I1940960);
124
125}
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