Rivet analyses referenceBESIII_2017_I1596897Cross Section for $e^+e^-\to\eta h_c$ for energies between 4.085 and 4.6 GeVExperiment: BESIII (BEPC) Inspire ID: 1596897 Status: VALIDATED Authors:
Beam energies: (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); (2.2, 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:
Cross section for $e^+e^-\to\eta h_c$ for energies between 4.085 and 4.6 GeV measured by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2017_I1596897.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 h_c
10 class BESIII_2017_I1596897 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1596897);
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(_nhc, 1, 1, 1);
25 for (const string& en : _nhc.binning().edges<0>()) {
26 const double end = std::stod(en)*MeV;
27 if (isCompatibleWithSqrtS(end)) {
28 _ecms = en;
29 break;
30 }
31 }
32 if (_ecms.empty())
33 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 /// Perform the per-event analysis
48 void analyze(const Event& event) {
49 const FinalState& fs = apply<FinalState>(event, "FS");
50 map<long,int> nCount;
51 int ntotal(0);
52 for (const Particle& p : fs.particles()) {
53 nCount[p.pid()] += 1;
54 ++ntotal;
55 }
56 const FinalState& ufs = apply<FinalState>(event, "UFS");
57 // loop over h_c
58 for (const Particle& hc : ufs.particles(Cuts::pid==10443)) {
59 if(hc.children().empty()) continue;
60 map<long,int> nRes = nCount;
61 int ncount = ntotal;
62 findChildren(hc,nRes,ncount);
63 bool matched = false;
64 // loop over eta
65 for(const Particle & eta : ufs.particles(Cuts::pid==221)) {
66 // check eta not child of h_c
67 Particle parent=eta;
68 while(!parent.parents().empty()) {
69 parent=parent.parents()[0];
70 if(parent.abspid()==10443) break;
71 }
72 if(fuzzyEquals(parent.momentum(),hc.momentum())) continue;
73 map<long,int> nRes2 = nRes;
74 int ncount2 = ncount;
75 findChildren(eta,nRes2,ncount2);
76 if(ncount2!=0) continue;
77 matched=true;
78 for(auto const & val : nRes2) {
79 if(val.second!=0) {
80 matched = false;
81 break;
82 }
83 }
84 if(matched) {
85 _nhc->fill(_ecms);
86 break;
87 }
88 }
89 if(matched) break;
90 }
91 }
92
93
94 /// Normalise histograms etc., after the run
95 void finalize() {
96 scale(_nhc, crossSection()/ sumOfWeights() /picobarn);
97 }
98
99 /// @}
100
101
102 /// @name Histograms
103 /// @{
104 BinnedHistoPtr<string> _nhc;
105 string _ecms;
106 /// @}
107
108
109 };
110
111
112 RIVET_DECLARE_PLUGIN(BESIII_2017_I1596897);
113
114}
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