Rivet analyses referenceSND_2019_I1726419Cross section for e+e−→π+π−π0η for energies below 2 GeVExperiment: SND (VEPP-2M) Inspire ID: 1726419 Status: VALIDATED Authors:
Beam energies: (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.8, 0.8); (0.8, 0.8); (0.8, 0.8); (0.8, 0.8); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (1.0, 1.0); (1.0, 1.0) GeV Run details:
Measurement of the cross section for e+e−→π+π−π0η, and the resonant sub-processes ωη, ϕη and a0(980)ρ, for energies below 2 GeV by the SND experiment. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: SND_2019_I1726419.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 SND pi+pi-pi0eta cross section
10 class SND_2019_I1726419 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2019_I1726419);
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 for(unsigned int ix=0;ix<4;++ix)
27 book(_sigma[ix], 1, 1, 1+ix);
28 for (const string& en : _sigma[0].binning().edges<0>()) {
29 double end = std::stod(en)*GeV;
30 if(isCompatibleWithSqrtS(end)) {
31 _ecms[0] = en;
32 if(end>1.6*GeV) _ecms[1]=en;
33 break;
34 }
35 }
36 if(_ecms[0].empty()) MSG_ERROR("Beam energy incompatible with analysis.");
37 }
38
39
40 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
41 for( const Particle &child : p.children()) {
42 if(child.children().empty()) {
43 --nRes[child.pid()];
44 --ncount;
45 }
46 else
47 findChildren(child,nRes,ncount);
48 }
49 }
50
51 /// Perform the per-event analysis
52 void analyze(const Event& event) {
53
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 bool found = false, foundOmegaPhi = false;
64 for (const Particle& p : ufs.particles(Cuts::pid==221)) {
65 map<long,int> nRes = nCount;
66 int ncount = ntotal;
67 findChildren(p,nRes,ncount);
68 // eta pi+pi-
69 if(ncount==3) {
70 bool matched = true;
71 for(auto const & val : nRes) {
72 if(abs(val.first)==211 || val.first==111 ) {
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 _sigma[0]->fill(_ecms[0]);
85 found = true;
86 }
87 }
88 for (const Particle& p2 : ufs.particles()) {
89 if(p2.pid()!=223 && p2.pid()!=333) continue;
90 map<long,int> nResB = nRes;
91 int ncountB = ncount;
92 findChildren(p2,nResB,ncountB);
93 if(ncountB!=0) continue;
94 bool matched2 = true;
95 for(auto const & val : nResB) {
96 if(val.second!=0) {
97 matched2 = false;
98 break;
99 }
100 }
101 if(matched2) {
102 if(p2.pid()==223)
103 _sigma[1]->fill(_ecms[0]);
104 else if(p2.pid()==333 && !_ecms[1].empty())
105 _sigma[2]->fill(_ecms[1]);
106 foundOmegaPhi=true;
107 }
108 }
109 }
110 if(found && !foundOmegaPhi)
111 _sigma[3]->fill(_ecms[0]);
112 }
113
114
115 /// Normalise histograms etc., after the run
116 void finalize() {
117 double fact = crossSection()/nanobarn/sumOfWeights();
118 for (unsigned int ix=0;ix<4;++ix) {
119 scale(_sigma[ix],fact);
120 }
121 }
122
123 /// @}
124
125
126 /// @name Histograms
127 /// @{
128 BinnedHistoPtr<string> _sigma[4];
129 string _ecms[2];
130 /// @}
131
132
133 };
134
135
136 RIVET_DECLARE_PLUGIN(SND_2019_I1726419);
137
138
139}
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