Rivet analyses referenceSND_2015_I1332929Cross section for $e^+e^-\to\eta\pi^+\pi^-$ between 1.22 and 2 GeVExperiment: SND (VEPP-2M) Inspire ID: 1332929 Status: VALIDATED Authors:
Beam energies: ANY Run details:
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 Add a short analysis description here
10 class SND_2015_I1332929 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2015_I1332929);
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, "TMP/EtaPiPi");
27 }
28
29 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
30 for (const Particle &child : p.children()) {
31 if(child.children().empty()) {
32 --nRes[child.pid()];
33 --ncount;
34 }
35 else
36 findChildren(child,nRes,ncount);
37 }
38 }
39
40
41 /// Perform the per-event analysis
42 void analyze(const Event& event) {
43 const FinalState& fs = apply<FinalState>(event, "FS");
44
45 map<long,int> nCount;
46 int ntotal(0);
47 for (const Particle& p : fs.particles()) {
48 nCount[p.pid()] += 1;
49 ++ntotal;
50 }
51 const FinalState& ufs = apply<FinalState>(event, "UFS");
52 for (const Particle& p : ufs.particles()) {
53 if(p.children().empty()) continue;
54 // find the eta
55 if(p.pid()==221) {
56 map<long,int> nRes = nCount;
57 int ncount = ntotal;
58 findChildren(p,nRes,ncount);
59 // eta pi+pi-
60 if(ncount!=2) continue;
61 bool matched = true;
62 for(auto const & val : nRes) {
63 if(abs(val.first)==211) {
64 if(val.second !=1) {
65 matched = false;
66 break;
67 }
68 }
69 else if(val.second!=0) {
70 matched = false;
71 break;
72 }
73 }
74 if(matched)
75 _numEtaPiPi->fill();
76 }
77 }
78 }
79
80
81 /// Normalise histograms etc., after the run
82 void finalize() {
83 double sigma = _numEtaPiPi->val();
84 double error = _numEtaPiPi->err();
85 sigma *= crossSection()/ sumOfWeights() /nanobarn;
86 error *= crossSection()/ sumOfWeights() /nanobarn;
87 Estimate1DPtr mult;
88 book(mult, 1, 1, 1);
89 for (auto& b : mult->bins()) {
90 if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
91 b.set(sigma, error);
92 }
93 }
94 }
95
96 /// @}
97
98
99 /// @name Histograms
100 /// @{
101 CounterPtr _numEtaPiPi;
102 /// @}
103
104
105 };
106
107
108 RIVET_DECLARE_PLUGIN(SND_2015_I1332929);
109
110
111}
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