Rivet analyses referenceBESIII_2022_I2512962Cross section for $e^+e^-\to\eta\Lambda\bar{\Lambda}$ from 3.51 to 4.7 GeVExperiment: BESIII (BEPC) Inspire ID: 2512962 Status: VALIDATED NOHEPDATA Authors:
Beam energies: (1.8, 1.8); (1.9, 1.9); (1.9, 1.9); (2.0, 2.0); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3) GeV Run details:
Measurement of the cross section for $e^+e^-\to\eta\Lambda\bar{\Lambda}$ from 3.51 to 4.7 GeV by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2022_I2512962.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/FinalState.hh"
5
6namespace Rivet {
7
8
9 /// @brief e+e- -> eta lambda lambda bar
10 class BESIII_2022_I2512962 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2512962);
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 // counter
27 book(_sigma,1,1,1);
28
29 for (const string& en : _sigma.binning().edges<0>()) {
30 const double end = std::stod(en)*GeV;
31 if (isCompatibleWithSqrtS(end)) {
32 _ecms = en;
33 break;
34 }
35 }
36 if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
37 }
38
39 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
40 for (const Particle &child : p.children()) {
41 if(child.children().empty()) {
42 nRes[child.pid()]-=1;
43 --ncount;
44 }
45 else {
46 findChildren(child,nRes,ncount);
47 }
48 }
49 }
50
51 /// Perform the per-event analysis
52 void analyze(const Event& event) {
53 const FinalState& fs = apply<FinalState>(event, "FS");
54
55 map<long,int> nCount;
56 int ntotal(0);
57 for (const Particle& p : fs.particles()) {
58 nCount[p.pid()] += 1;
59 ++ntotal;
60 }
61 const FinalState& ufs = apply<FinalState>(event, "UFS");
62 // loop over eta mesons
63 for (const Particle& eta : ufs.particles(Cuts::pid==221)) {
64 bool matched = false;
65 map<long,int> nRes=nCount;
66 int ncount = ntotal;
67 findChildren(eta,nRes,ncount);
68 // then Lambda baryons
69 for (const Particle& lambda : ufs.particles(Cuts::pid==3122)) {
70 map<long,int> nResB = nRes;
71 int ncountB = ncount;
72 findChildren(lambda,nResB,ncountB);
73 for (const Particle& lambar : ufs.particles(Cuts::pid==-3122)) {
74 map<long,int> nResC = nResB;
75 int ncountC = ncountB;
76 findChildren(lambar,nResC,ncountC);
77 matched=true;
78 for (const auto& val : nResC) {
79 if (val.second!=0) {
80 matched = false;
81 break;
82 }
83 }
84 if (matched) {
85 _sigma->fill(_ecms);
86 break;
87 }
88 }
89 if (matched) break;
90 }
91 if (matched) break;
92 }
93 }
94
95
96 /// Normalise histograms etc., after the run
97 void finalize() {
98 scale(_sigma,crossSection()/ sumOfWeights() /picobarn);
99 }
100
101 /// @}
102
103
104 /// @name Histograms
105 /// @{
106 BinnedHistoPtr<string> _sigma;
107 string _ecms;
108 /// @}
109
110
111 };
112
113
114 RIVET_DECLARE_PLUGIN(BESIII_2022_I2512962);
115
116}
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