Rivet analyses referenceBESIII_2023_I2711200Cross section for $e^+e^-\to\pi^+\pi^-\eta$ between 2.00 and 3.08 GeVExperiment: BESIII (BEPC) Inspire ID: 2711200 Status: VALIDATED NOHEPDATA Authors:
Beam energies: (1.0, 1.0); (1.0, 1.0); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (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); (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 $e^+e^-\to\pi^+\pi^-\eta$ between 3.872 and 4.7 GeV by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2023_I2711200.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- -> pi+pi-eta
10 class BESIII_2023_I2711200 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2711200);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 declare(FinalState(), "FS");
23 declare(UnstableParticles(), "UFS");
24 for(unsigned int ix=0;ix<3;++ix)
25 book(_sigma[ix] , 1+ix,1,1);
26 for (const string& en : _sigma[0].binning().edges<0>()) {
27 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()];
40 --ncount;
41 }
42 else {
43 findChildren(child,nRes,ncount);
44 }
45 }
46 }
47
48 /// Perform the per-event analysis
49 void analyze(const Event& event) {
50 const FinalState& fs = apply<FinalState>(event, "FS");
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 const FinalState& ufs = apply<FinalState>(event, "UFS");
58 // loop over eta mesons
59 for (const Particle& p : ufs.particles(Cuts::pid==221)) {
60 map<long,int> nRes = nCount;
61 int ncount = ntotal;
62 findChildren(p,nRes,ncount);
63 bool matched = true;
64 for (const auto& val : nRes) {
65 if (abs(val.first)==211) {
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) continue;
77 _sigma[0]->fill(_ecms);
78 for (const Particle& p2 : ufs.particles(Cuts::pid==113)) {
79 map<long,int> nResB = nRes;
80 int ncountB = ncount;
81 findChildren(p2,nResB,ncountB);
82 if (ncountB!=0) continue;
83 bool matched = true;
84 for (const auto& val : nResB) {
85 if (val.second!=0) {
86 matched = false;
87 break;
88 }
89 }
90 if(matched) _sigma[1]->fill(_ecms);
91 }
92 }
93 // loop over a_2 mesons
94 for (const Particle& p : ufs.particles(Cuts::abspid==215 || Cuts::pid == 115)) {
95 map<long,int> nRes = nCount;
96 int ncount = ntotal;
97 findChildren(p,nRes,ncount);
98 bool matched = true;
99 int ipi=111;
100 if (p.abspid()==215) ipi=211*p.pid()/p.abspid();
101 for (const auto& val : nRes) {
102 if (abs(val.first)==ipi) {
103 if (val.second !=1) {
104 matched = false;
105 break;
106 }
107 }
108 else if (val.second!=0) {
109 matched = false;
110 break;
111 }
112 }
113 if (matched) {
114 _sigma[2]->fill(_ecms);
115 break;
116 }
117 }
118 }
119
120
121 /// Normalise histograms etc., after the run
122 void finalize() {
123 double fact = crossSection()/ sumOfWeights() /picobarn;
124 for(unsigned int ix=0;ix<3;++ix) {
125 scale(_sigma[ix],fact);
126 }
127 }
128
129 /// @}
130
131
132 /// @name Histograms
133 /// @{
134 BinnedHistoPtr<string> _sigma[3];
135 string _ecms;
136 /// @}
137
138
139 };
140
141
142 RIVET_DECLARE_PLUGIN(BESIII_2023_I2711200);
143
144}
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