Rivet analyses referenceBESIII_2024_I2751832Cross section for $e^+e^-\to\pi^+\pi^-\pi^0$ between 2.00 and 3.08 GeVExperiment: BESIII (BEPC) Inspire ID: 2751832 Status: VALIDATED NOHEPDATA 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:
Cross section for $e^+e^-\to\pi^+\pi^-\pi^0$ between 2.00 and 3.08 GeV measured by BESII. The $\rho\pi$ and $\rho(1450)\pi$ subprocesses are also extracted. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2024_I2751832.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- pi0
10 class BESIII_2024_I2751832 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2751832);
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 for(unsigned int ix=0;ix<3;++ix)
26 book(_sigma[ix], 1, 1, 1+ix);
27
28 for (const string& en : _sigma[0].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()) 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()];
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
53 const FinalState& fs = apply<FinalState>(event, "FS");
54
55 map<long,int> nCount;
56 int ntotal(0);
57 Particle pip, pim;
58 for (const Particle& p : fs.particles()) {
59 nCount[p.pid()] += 1;
60 ++ntotal;
61 if (p.pid() == 211) pip=p;
62 else if (p.pid()==-211) pim=p;
63 }
64 if (ntotal!=3) vetoEvent;
65 if (nCount[-211]==1&&nCount[211]==1&&nCount[111]==1) {
66 _sigma[0]->fill(_ecms);
67 }
68 else {
69 vetoEvent;
70 }
71 const FinalState& ufs = apply<FinalState>(event, "UFS");
72 for (const Particle& p : ufs.particles(Cuts::abspid==113 || Cuts::abspid==213 ||
73 Cuts::abspid==100113 || Cuts::abspid==100213)) {
74 if (p.children().empty()) continue;
75 map<long,int> nRes = nCount;
76 int ncount = ntotal;
77 findChildren(p,nRes,ncount);
78 if (ncount!=1) continue;
79 int idOther = 211;
80 if (p.pid()==113 || p.pid()==100113) {
81 idOther = 111;
82 }
83 else if (p.pid()==213 || p.pid()==100213) {
84 idOther = -211;
85 }
86 bool matched=true;
87 for (const auto& val : nRes) {
88 if (val.first==idOther) {
89 if (val.second !=1) {
90 matched = false;
91 break;
92 }
93 }
94 else if (val.second!=0) {
95 matched = false;
96 break;
97 }
98 }
99 if (!matched) continue;
100 if (matched) {
101 if (p.pid()==213 || p.pid()==113)
102 _sigma[1]->fill(_ecms);
103 else
104 _sigma[2]->fill(_ecms);
105 break;
106 }
107 }
108 }
109
110
111 /// Normalise histograms etc., after the run
112 void finalize() {
113 double fact = crossSection()/picobarn/sumOfWeights();
114 for(unsigned int ix=0;ix<3;++ix)
115 scale(_sigma[ix],fact);
116 }
117
118 /// @}
119
120
121 /// @name Histograms
122 /// @{
123 BinnedHistoPtr<string> _sigma[3];
124 string _ecms;
125 /// @}
126
127
128 };
129
130
131 RIVET_DECLARE_PLUGIN(BESIII_2024_I2751832);
132
133}
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