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: 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 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, "TMP/OmegaPi");
27 }
28
29
30
31 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
32 for (const Particle &child : p.children()) {
33 if(child.children().empty()) {
34 nRes[child.pid()]+=1;
35 ++ncount;
36 }
37 else
38 findChildren(child,nRes,ncount);
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 // three particles (pi0 pi0 gamma)
52 if(ntotal!=3) vetoEvent;
53 const FinalState& ufs = apply<FinalState>(event, "UFS");
54 for (const Particle& p : ufs.particles()) {
55 if(p.children().empty()) continue;
56 // find the omega
57 if(p.pid()==223) {
58 map<long,int> nRes;
59 int ncount(0);
60 findChildren(p,nRes,ncount);
61 // only omega to pi0 gamma mode
62 if(ncount!=2) continue;
63 if(nRes[111]!=1 || nRes[22]!=1) continue;
64 // omega pi0
65 if(nCount[111]-nRes[111]==1)
66 _numOmegaPi->fill();
67 }
68 }
69 }
70
71
72 /// Normalise histograms etc., after the run
73 void finalize() {
74
75 double sigma = _numOmegaPi->val();
76 double error = _numOmegaPi->err();
77 sigma *= crossSection()/ sumOfWeights() /nanobarn;
78 error *= crossSection()/ sumOfWeights() /nanobarn;
79 Scatter2D temphisto(refData(1, 1, 1));
80 Scatter2DPtr mult;
81 book(mult, 1, 1, 1);
82 for (size_t b = 0; b < temphisto.numPoints(); b++) {
83 const double x = temphisto.point(b).x();
84 pair<double,double> ex = temphisto.point(b).xErrs();
85 pair<double,double> ex2 = ex;
86 if(ex2.first ==0.) ex2. first=0.0001;
87 if(ex2.second==0.) ex2.second=0.0001;
88 if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
89 mult->addPoint(x, sigma, ex, make_pair(error,error));
90 }
91 else {
92 mult->addPoint(x, 0., ex, make_pair(0.,.0));
93 }
94 }
95 }
96
97 //@}
98
99 /// @name Histograms
100 //@{
101 CounterPtr _numOmegaPi;
102 //@}
103
104
105 };
106
107
108 // The hook for the plugin system
109 RIVET_DECLARE_PLUGIN(SND_2016_I1489182);
110
111
112}
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