Rivet analyses referenceBESIII_2021_I1859248Cross section for e+e−→ϕΛˉΛ from 3.51 to 4.6 GeVExperiment: BESIII (BEPC) Inspire ID: 1859248 Status: VALIDATED Authors:
Beam energies: (1.8, 1.8); (1.9, 1.9); (1.9, 1.9); (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); (2.1, 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); (2.3, 2.3); (2.3, 2.3) GeV Run details:
Measurement of the cross section for e+e−→ϕΛˉΛ from 3.51 to 4.6 GeV by the BESIII collaboration. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2021_I1859248.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/FinalState.hh"
5
6namespace Rivet {
7
8
9 /// @brief e+e- -> phi lambda lambda bar
10 class BESIII_2021_I1859248 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1859248);
15
16
17 /// @name Analysis methods
18 ///@{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22
23 // Initialise and register projections
24 declare(FinalState(), "FS");
25 declare(UnstableParticles(), "UFS");
26 // counter
27 book(_c_phiLL, 1, 1, 1);
28 for (const string& en : _c_phiLL.binning().edges<0>()) {
29 const double end = std::stod(en)*MeV;
30 if (isCompatibleWithSqrtS(end)) {
31 _ecms = en;
32 break;
33 }
34 }
35 if (_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
36 }
37
38 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
39 for (const Particle &child : p.children()) {
40 if (child.children().empty()) {
41 nRes[child.pid()]-=1;
42 --ncount;
43 }
44 else {
45 findChildren(child,nRes,ncount);
46 }
47 }
48 }
49
50 /// Perform the per-event analysis
51 void analyze(const Event& event) {
52 const FinalState& fs = apply<FinalState>(event, "FS");
53
54 map<long,int> nCount;
55 int ntotal(0);
56 for (const Particle& p : fs.particles()) {
57 nCount[p.pid()] += 1;
58 ++ntotal;
59 }
60 const FinalState& ufs = apply<FinalState>(event, "UFS");
61 // loop over phi mesons
62 for (const Particle& phi : ufs.particles(Cuts::pid==333)) {
63 bool matched = false;
64 map<long,int> nRes=nCount;
65 int ncount = ntotal;
66 findChildren(phi,nRes,ncount);
67 // then Lambda baryons
68 for (const Particle& lambda : ufs.particles(Cuts::pid==3122)) {
69 map<long,int> nResB = nRes;
70 int ncountB = ncount;
71 findChildren(lambda,nResB,ncountB);
72 for (const Particle& lambar : ufs.particles(Cuts::pid==-3122)) {
73 map<long,int> nResC = nResB;
74 int ncountC = ncountB;
75 findChildren(lambar,nResC,ncountC);
76 matched=true;
77 for (const auto& val : nResC) {
78 if (val.second!=0) {
79 matched = false;
80 break;
81 }
82 }
83 if (matched) {
84 _c_phiLL->fill(_ecms);
85 break;
86 }
87 }
88 if (matched) break;
89 }
90 if (matched) break;
91 }
92 }
93
94
95 /// Normalise histograms etc., after the run
96 void finalize() {
97 scale(_c_phiLL, crossSection()/ sumOfWeights() /picobarn);
98 }
99
100 ///@}
101
102
103 /// @name Histograms
104 ///@{
105 BinnedHistoPtr<string> _c_phiLL;
106 string _ecms;
107 ///@}
108
109
110 };
111
112
113 RIVET_DECLARE_PLUGIN(BESIII_2021_I1859248);
114
115}
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