Rivet analyses referenceBESIII_2020_I1836509Cross section for $e^+e^-\to\eta^\prime\pi^+\pi^-$ for energies between 2.00 and 3.08 GeVExperiment: BESIII (BEPC) Inspire ID: 1836509 Status: VALIDATED Authors:
Beam energies: (1.0, 1.0); (1.0, 1.0); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.2, 1.2); (1.2, 1.2); (1.2, 1.2); (1.3, 1.3); (1.3, 1.3); (1.4, 1.4); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5); (1.5, 1.5) GeV Run details:
Measurement of the cross section for $e^+e^-\to\eta^\prime\pi^+\pi^-$ for energies between 2.00 and 3.08 GeV by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2020_I1836509.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- > pi+pi- eta'
10 class BESIII_2020_I1836509 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1836509);
15
16
17 /// @name Analysis methods
18 ///@{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // Initialise and register projections
23 declare(FinalState(), "FS");
24 declare(UnstableParticles(), "UFS");
25 // histograms
26 book(_nPiPiEta, 1, 1, 1);
27 for (const string& en : _nPiPiEta.binning().edges<0>()) {
28 const double end = std::stod(en)*GeV;
29 if (isCompatibleWithSqrtS(end)) {
30 _ecms = en;
31 break;
32 }
33 }
34 if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
35 }
36
37 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
38 for(const Particle &child : p.children()) {
39 if(child.children().empty()) {
40 nRes[child.pid()]-=1;
41 --ncount;
42 }
43 else
44 findChildren(child,nRes,ncount);
45 }
46 }
47
48 /// Perform the per-event analysis
49 void analyze(const Event& event) {
50 const FinalState& fs = apply<FinalState>(event, "FS");
51
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==331)) {
60 if(p.children().empty()) continue;
61 map<long,int> nRes = nCount;
62 int ncount = ntotal;
63 findChildren(p,nRes,ncount);
64 if(ncount!=2) continue;
65 bool matched = true;
66 for(auto const & val : nRes) {
67 if(abs(val.first)==211) {
68 if(val.second!=1) {
69 matched = false;
70 break;
71 }
72 }
73 else if(val.second!=0) {
74 matched = false;
75 break;
76 }
77 }
78 if(matched) _nPiPiEta->fill(_ecms);
79 }
80 }
81
82
83 /// Normalise histograms etc., after the run
84 void finalize() {
85 scale(_nPiPiEta, crossSection()/ sumOfWeights() /picobarn);
86 }
87 ///@}
88
89
90 /// @name Histograms
91 ///@{
92 BinnedHistoPtr<string> _nPiPiEta;
93 string _ecms;
94 ///@}
95
96
97 };
98
99
100 RIVET_DECLARE_PLUGIN(BESIII_2020_I1836509);
101
102}
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