Rivet analyses referenceBESIII_2023_I2688408Cross Section for $e^+e^-\to\phi\pi^+\pi^-$ between 2 and $3.08$ GeVExperiment: BESIII (BEPC) Inspire ID: 2688408 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); (1.2, 1.2); (1.3, 1.3); (1.3, 1.3); (1.4, 1.4); (1.4, 1.4); (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 $e^+e^-\to\phi\pi^+\pi^-$ for energies between 2 and $3.08$ GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2023_I2688408.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- -> phi pi+ pi-
10 class BESIII_2023_I2688408 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2688408);
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(_cphipippim, 1, 1, 1);
28 for(const string& en : _cphipippim.binning().edges<0>()) {
29 double end = std::stod(en)*GeV;
30 if(isCompatibleWithSqrtS(end)) {
31 _ecms = en;
32 break;
33 }
34 }
35 if( _ecms.empty() )
36 MSG_ERROR("Beam energy incompatible with analysis.");
37 }
38
39 void findChildren(const Particle& p,map<long,int>& nRes, int& ncount) {
40 for (const Particle &child : p.children()) {
41 if (child.children().empty()) {
42 nRes[child.pid()]-=1;
43 --ncount;
44 }
45 else {
46 findChildren(child,nRes,ncount);
47 }
48 }
49 }
50
51
52 /// Perform the per-event analysis
53 void analyze(const Event& event) {
54 const FinalState& fs = apply<FinalState>(event, "FS");
55
56 map<long,int> nCount;
57 int ntotal(0);
58 for (const Particle& p : fs.particles()) {
59 nCount[p.pid()] += 1;
60 ++ntotal;
61 }
62 const FinalState& ufs = apply<FinalState>(event, "UFS");
63 for (const Particle& p : ufs.particles(Cuts::pid==PID::PHI)) {
64 if (p.children().empty()) continue;
65 map<long,int> nRes=nCount;
66 int ncount = ntotal;
67 findChildren(p,nRes,ncount);
68 // phi pi+pi-
69 if (ncount==2) {
70 bool matched = true;
71 for (const auto& val : nRes) {
72 if (abs(val.first)==211) {
73 if (val.second!=1) {
74 matched = false;
75 break;
76 }
77 }
78 else if (val.second!=0) {
79 matched = false;
80 break;
81 }
82 }
83 if (matched) {
84 _cphipippim->fill(_ecms);
85 break;
86 }
87 }
88 }
89 }
90
91
92 /// Normalise histograms etc., after the run
93 void finalize() {
94 scale(_cphipippim, crossSection()/ sumOfWeights() /picobarn);
95 }
96
97 /// @}
98
99
100 /// @name Histograms
101 /// @{
102 BinnedHistoPtr<string> _cphipippim;
103 string _ecms;
104 /// @}
105
106
107 };
108
109
110 RIVET_DECLARE_PLUGIN(BESIII_2023_I2688408);
111
112}
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