Rivet analyses referenceBESIII_2016_I1457597Cross section for $e^+e^-\to J/\psi \eta^\prime$ at energies between 4.189 and 4.6 GeVExperiment: BESIII (BEPC) Inspire ID: 1457597 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the cross section for $e^+e^-\to J/\psi \eta^\prime$ at energies between 4.189 and 4.6 GeV Source code: BESIII_2016_I1457597.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 Cross section for $e^+e^-\to J/\psi \eta^\prime$ at energies between 4.189 and 4.6 GeV
10 class BESIII_2016_I1457597 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2016_I1457597);
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(_nJPsi, "TMP/jpsi");
25 }
26
27 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
28 for(const Particle &child : p.children()) {
29 if(child.children().empty()) {
30 --nRes[child.pid()];
31 --ncount;
32 }
33 else
34 findChildren(child,nRes,ncount);
35 }
36 }
37
38 /// Perform the per-event analysis
39 void analyze(const Event& event) {
40 const FinalState& fs = apply<FinalState>(event, "FS");
41 map<long,int> nCount;
42 int ntotal(0);
43 for (const Particle& p : fs.particles()) {
44 nCount[p.pid()] += 1;
45 ++ntotal;
46 }
47 const FinalState& ufs = apply<FinalState>(event, "UFS");
48 for (const Particle& p1 : ufs.particles()) {
49 bool matched=false;
50 if(p1.children().empty()) continue;
51 // find the j/psi
52 if(p1.pid()!=443) continue;
53 map<long,int> nRes = nCount;
54 int ncount = ntotal;
55 findChildren(p1,nRes,ncount);
56
57 for (const Particle& p2 : ufs.particles()) {
58 if(p2.children().empty()) continue;
59 // find the j/psi
60 if(p2.pid()!=331) continue;
61 map<long,int> nRes2 = nRes;
62 int ncount2 = ncount;
63 findChildren(p2,nRes2,ncount2);
64 if(ncount2!=0) continue;
65 matched=true;
66 for(auto const & val : nRes2) {
67 if(val.second!=0) {
68 matched = false;
69 break;
70 }
71 }
72 if(matched) {
73 _nJPsi->fill();
74 break;
75 }
76 }
77 if(matched) break;
78 }
79 }
80
81 /// Normalise histograms etc., after the run
82 void finalize() {
83 double sigma = _nJPsi->val();
84 double error = _nJPsi->err();
85 sigma *= crossSection()/ sumOfWeights() /picobarn;
86 error *= crossSection()/ sumOfWeights() /picobarn;
87 Estimate1DPtr mult;
88 book(mult, 1, 1, 7);
89 for (auto& b : mult->bins()) {
90 if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
91 b.set(sigma, error, "stat");
92 }
93 }
94 }
95
96 /// @}
97
98
99 /// @name Histograms
100 /// @{
101 CounterPtr _nJPsi;
102 /// @}
103
104
105 };
106
107
108 RIVET_DECLARE_PLUGIN(BESIII_2016_I1457597);
109
110
111}
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