Rivet analyses referenceSND_2018_I1638368Cross section for $e^+e^-\to\eta\pi^+\pi^-$ between 1.08 and 2 GeVExperiment: SND (VEPP-2M) Inspire ID: 1638368 Status: VALIDATED Authors:
Beam energies: (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); (0.7, 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); (0.9, 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) GeV Run details:
Measurement of the cross section for $e^+e^-\to\eta\pi^+\pi^-$ at energies between 1.08 and 2 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: SND_2018_I1638368.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- -> eta pi+pi-
10 class SND_2018_I1638368 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2018_I1638368);
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(_numEtaPiPi, 1,1,1);
27 for (const string& en : _numEtaPiPi.binning().edges<0>()) {
28 double end = std::stod(en)*GeV;
29 if(isCompatibleWithSqrtS(end)) {
30 _ecms = en;
31 break;
32 }
33 }
34 if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
35 }
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 /// 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 const FinalState& ufs = apply<FinalState>(event, "UFS");
60 for (const Particle& p : ufs.particles()) {
61 if(p.children().empty()) continue;
62 // find the omega
63 if(p.pid()==221) {
64 map<long,int> nRes = nCount;
65 int ncount = ntotal;
66 findChildren(p,nRes,ncount);
67 // eta pi+pi-
68 if(ncount!=2) continue;
69 bool matched = true;
70 for(auto const & val : nRes) {
71 if(abs(val.first)==211) {
72 if(val.second !=1) {
73 matched = false;
74 break;
75 }
76 }
77 else if(val.second!=0) {
78 matched = false;
79 break;
80 }
81 }
82 if(matched)
83 _numEtaPiPi->fill(_ecms);
84 }
85 }
86 }
87
88
89 /// Normalise histograms etc., after the run
90 void finalize() {
91 double fact = crossSection()/ sumOfWeights() /nanobarn;
92 scale(_numEtaPiPi,fact);
93 }
94
95 /// @}
96
97
98 /// @name Histograms
99 /// @{
100 BinnedHistoPtr<string> _numEtaPiPi;
101 string _ecms;
102 /// @}
103
104
105 };
106
107
108 RIVET_DECLARE_PLUGIN(SND_2018_I1638368);
109
110
111}
|