Rivet analyses referenceSND_2016_I1489182Cross section for $e^+e^-\to\omega\pi^0\to\pi^0\pi^0\gamma$ between 1.05 and 2 GeVExperiment: SND (VEPP-2M) Inspire ID: 1489182 Status: VALIDATED Authors:
Beam energies: (0.5, 0.5); (0.5, 0.5); (0.5, 0.5); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.6, 0.6); (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (0.7, 0.7); (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); (0.8, 0.8); (0.8, 0.8); (0.8, 0.8); (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); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (0.9, 0.9); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0) GeV Run details:
Measurement of the cross section for $e^+e^-\to\omega\pi^0\to\pi^0\pi^0\gamma$ at energies between 1.05 and 2 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: SND_2016_I1489182.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- > omega pi
10 class SND_2016_I1489182 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2016_I1489182);
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 book(_numOmegaPi, 1, 1, 1);
27
28 for (const string& en : _numOmegaPi.binning().edges<0>()) {
29 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 /// Perform the per-event analysis
50 void analyze(const Event& event) {
51 const FinalState& fs = apply<FinalState>(event, "FS");
52
53 map<long,int> nCount;
54 int ntotal(0);
55 for (const Particle& p : fs.particles()) {
56 nCount[p.pid()] += 1;
57 ++ntotal;
58 }
59 // three particles (pi0 pi0 gamma)
60 if(ntotal!=3) vetoEvent;
61 const FinalState& ufs = apply<FinalState>(event, "UFS");
62 for (const Particle& p : ufs.particles()) {
63 if(p.children().empty()) continue;
64 // find the omega
65 if(p.pid()==223) {
66 map<long,int> nRes;
67 int ncount(0);
68 findChildren(p,nRes,ncount);
69 // only omega to pi0 gamma mode
70 if(ncount!=2) continue;
71 if(nRes[111]!=1 || nRes[22]!=1) continue;
72 // omega pi0
73 if(nCount[111]-nRes[111]==1)
74 _numOmegaPi->fill(_ecms);
75 }
76 }
77 }
78
79
80 /// Normalise histograms etc., after the run
81 void finalize() {
82 scale(_numOmegaPi, crossSection()/ sumOfWeights() /nanobarn);
83 }
84
85 /// @}
86
87 /// @name Histograms
88 /// @{
89 BinnedHistoPtr<string> _numOmegaPi;
90 string _ecms;
91 /// @}
92
93
94 };
95
96
97 RIVET_DECLARE_PLUGIN(SND_2016_I1489182);
98
99
100}
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