Rivet analyses referenceBESIII_2022_I2068180Cross section for $e^+e^-\to J/\psi K^+K^-$ at energies between 4.127 and 4.6 GeVExperiment: BESIII (BEPC) Inspire ID: 2068180 Status: VALIDATED NOHEPDATA No authors listed References:
Beam energies: (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); (2.1, 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); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3) GeV Run details:
Measurement of the cross section for $e^+e^-\to J/\psi K^+K^-$ at energies between 4.127 and 4.6 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2022_I2068180.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- > K+K- J/psi
10 class BESIII_2022_I2068180 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2068180);
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 book(_sigmaPsi, 1, 1, 1);
25
26 for (const string& en : _sigmaPsi.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()];
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 // find the psis
59 for (const Particle& p : ufs.particles(Cuts::pid==443)) {
60 if (p.children().empty()) continue;
61 map<long,int> nRes = nCount;
62 int ncount = ntotal;
63 findChildren(p,nRes,ncount);
64 // psi pi+pi-
65 if (ncount!=2) continue;
66 bool matched = true;
67 for (const auto& val : nRes) {
68 if (abs(val.first)==321) {
69 if (val.second !=1) {
70 matched = false;
71 break;
72 }
73 }
74 else if (val.second!=0) {
75 matched = false;
76 break;
77 }
78 }
79 if (matched) {
80 _sigmaPsi->fill(_ecms);
81 break;
82 }
83 }
84 }
85
86
87 /// Normalise histograms etc., after the run
88 void finalize() {
89 scale(_sigmaPsi, crossSection()/ sumOfWeights() /picobarn);
90 }
91
92 /// @}
93
94
95 /// @name Histograms
96 /// @{
97 BinnedHistoPtr<string> _sigmaPsi;
98 string _ecms;
99 /// @}
100
101
102 };
103
104
105 RIVET_DECLARE_PLUGIN(BESIII_2022_I2068180);
106
107}
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