Rivet analyses referenceDM2_1988_I264144Cross section for $e^+e^-\to\eta\pi^+\pi^-$ at energies between 1.35 and 2.4 GeVExperiment: DM2 (DCI) Inspire ID: 264144 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 DM2_1988_I264144 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(DM2_1988_I264144);
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 /// Perform the per-event analysis
41 void analyze(const Event& event) {
42 const FinalState& fs = apply<FinalState>(event, "FS");
43
44 map<long,int> nCount;
45 int ntotal(0);
46 for (const Particle& p : fs.particles()) {
47 nCount[p.pid()] += 1;
48 ++ntotal;
49 }
50 const FinalState& ufs = apply<FinalState>(event, "UFS");
51 for (const Particle& p : ufs.particles()) {
52 if(p.children().empty()) continue;
53 // find the omega
54 if(p.pid()==221) {
55 map<long,int> nRes = nCount;
56 int ncount = ntotal;
57 findChildren(p,nRes,ncount);
58 // eta pi+pi-
59 if(ncount!=2) continue;
60 bool matched = true;
61 for(auto const & val : nRes) {
62 if(abs(val.first)==211) {
63 if(val.second !=1) {
64 matched = false;
65 break;
66 }
67 }
68 else if(val.second!=0) {
69 matched = false;
70 break;
71 }
72 }
73 if(matched)
74 _numEtaPiPi->fill();
75 }
76 }
77 }
78
79
80 /// Normalise histograms etc., after the run
81 void finalize() {
82 double sigma = _numEtaPiPi->val();
83 double error = _numEtaPiPi->err();
84 sigma *= crossSection()/ sumOfWeights() /nanobarn;
85 error *= crossSection()/ sumOfWeights() /nanobarn;
86 Scatter2D temphisto(refData(1, 1, 1));
87 Scatter2DPtr mult;
88 book(mult, 1, 1, 1);
89 for (size_t b = 0; b < temphisto.numPoints(); b++) {
90 const double x = temphisto.point(b).x();
91 pair<double,double> ex = temphisto.point(b).xErrs();
92 pair<double,double> ex2 = ex;
93 if(ex2.first ==0.) ex2. first=0.0001;
94 if(ex2.second==0.) ex2.second=0.0001;
95 if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
96 mult->addPoint(x, sigma, ex, make_pair(error,error));
97 }
98 else {
99 mult->addPoint(x, 0., ex, make_pair(0.,.0));
100 }
101 }
102 }
103
104 //@}
105
106
107 /// @name Histograms
108 //@{
109 CounterPtr _numEtaPiPi;
110 //@}
111
112
113 };
114
115
116 // The hook for the plugin system
117 RIVET_DECLARE_PLUGIN(DM2_1988_I264144);
118
119
120}
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