Rivet analyses referenceBESIII_2024_I2771682Cross Section for $e^+e^-\to\eta \psi(2S)$ for energies between 4.288 to 4.951 GeVExperiment: BESIII (BEPC) Inspire ID: 2771682 Status: VALIDATED NOHEPDATA Authors:
Beam energies: (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.5, 2.5); (2.5, 2.5) GeV Run details:
Cross section for $e^+e^-\to\eta \psi(2S)$ for energies between 4.288 and 4.951 GeV measured by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2024_I2771682.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- -> eta psi(2S)
10 class BESIII_2024_I2771682 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2771682);
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(_sigma, 1, 1, 1);
25
26 for (const string& en : _sigma.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
49 /// Perform the per-event analysis
50 void analyze(const Event& event) {
51 const FinalState& fs = apply<FinalState>(event, "FS");
52 map<long,int> nCount;
53 int ntotal(0);
54 for (const Particle& p : fs.particles()) {
55 nCount[p.pid()] += 1;
56 ++ntotal;
57 }
58 const FinalState& ufs = apply<FinalState>(event, "UFS");
59 for (const Particle& p : ufs.particles(Cuts::pid==PID::PSI2S)) {
60 if (p.children().empty()) continue;
61 // find the psi(2s)
62 map<long,int> nRes = nCount;
63 int ncount = ntotal;
64 findChildren(p,nRes,ncount);
65 bool matched=false;
66 for (const Particle& p2 : ufs.particles(Cuts::pid==PID::ETA)) {
67 if (p2.children().empty()) continue;
68 bool psi2SParent=false;
69 Particle parent=p2;
70 while (!parent.parents().empty()) {
71 parent=parent.parents()[0];
72 if (parent.pid()==PID::PSI2S) {
73 psi2SParent=true;
74 break;
75 }
76 }
77 if (psi2SParent) continue;
78 map<long,int> nRes2 = nRes;
79 int ncount2 = ncount;
80 findChildren(p2,nRes2,ncount2);
81 if (ncount2!=0) continue;
82 matched = true;
83 for (const auto& val : nRes2) {
84 if (val.second!=0) {
85 matched = false;
86 break;
87 }
88 }
89 if (matched) {
90 _sigma->fill(_ecms);
91 break;
92 }
93 }
94 if (matched) break;
95 }
96 }
97
98
99 /// Normalise histograms etc., after the run
100 void finalize() {
101 scale(_sigma,crossSection()/ sumOfWeights() /picobarn);
102 }
103
104 /// @}
105
106
107 /// @name Histograms
108 /// @{
109 BinnedHistoPtr<string> _sigma;
110 string _ecms;
111 /// @}
112
113
114 };
115
116
117 RIVET_DECLARE_PLUGIN(BESIII_2024_I2771682);
118
119}
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