Rivet analyses referenceBESIII_2021_I1866233Cross section for $e^+e^-\to\Xi^0\bar{\Xi}^0$ between 2.644 and 3.080 GeVExperiment: BESIII (BEPC) Inspire ID: 1866233 Status: VALIDATED Authors:
Beam energies: (1.3, 1.3); (1.3, 1.3); (1.4, 1.4); (1.4, 1.4); (1.4, 1.4); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5) GeV Run details:
Measurement of the cross section for $e^+e^-\to\Xi^0\bar{\Xi}^0$ between 2.644 and 3.080. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2021_I1866233.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 Xi0 Xibar0 cross section
10 class BESIII_2021_I1866233 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1866233);
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(_nXi, 1, 1, 1);
26 for (const string& en : _nXi.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(unsigned int ix=0;ix<ufs.particles().size();++ix) {
60 const Particle& p1 = ufs.particles()[ix];
61 if(abs(p1.pid())!=3322) continue;
62 bool matched = false;
63 // check fs
64 bool fs = true;
65 for(const Particle & child : p1.children()) {
66 if(child.pid()==p1.pid()) {
67 fs = false;
68 break;
69 }
70 }
71 if(!fs) continue;
72 // find the children
73 map<long,int> nRes = nCount;
74 int ncount = ntotal;
75 findChildren(p1,nRes,ncount);
76 for(unsigned int iy=ix+1;iy<ufs.particles().size();++iy) {
77 const Particle& p2 = ufs.particles()[iy];
78 if(abs(p2.pid())!=3322) continue;
79 // check fs
80 bool fs = true;
81 for(const Particle & child : p2.children()) {
82 if(child.pid()==p2.pid()) {
83 fs = false;
84 break;
85 }
86 }
87 if(!fs) continue;
88 map<long,int> nRes2 = nRes;
89 int ncount2 = ncount;
90 findChildren(p2,nRes2,ncount2);
91 if(ncount2!=0) continue;
92 matched=true;
93 for(auto const & val : nRes2) {
94 if(val.second!=0) {
95 matched = false;
96 break;
97 }
98 }
99 if(matched) {
100 _nXi->fill(_ecms);
101 break;
102 }
103 }
104 if(matched) break;
105 }
106 }
107
108
109 /// Normalise histograms etc., after the run
110 void finalize() {
111 scale(_nXi, crossSection()/ sumOfWeights() /picobarn);
112 }
113
114 ///@}
115
116
117 /// @name Histograms
118 ///@{
119 BinnedHistoPtr<string> _nXi;
120 string _ecms;
121 ///@}
122
123
124 };
125
126
127 RIVET_DECLARE_PLUGIN(BESIII_2021_I1866233);
128
129}
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