Rivet analyses referenceSND_2000_I527752Cross section for $e^+e^-\to\omega\pi^0\to\pi^0\pi^0\gamma$ for energies below 1.4 GeVExperiment: SND (VEPP-2M) Inspire ID: 527752 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_2000_I527752 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2000_I527752);
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 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()]+=1;
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 // 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 Estimate1DPtr mult;
80 book(mult, 1, 1, 1);
81 for (auto& b : mult->bins()) {
82 if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
83 b.set(sigma, error);
84 }
85 }
86 }
87
88 /// @}
89
90 /// @name Histograms
91 /// @{
92 CounterPtr _numOmegaPi;
93 /// @}
94
95
96 };
97
98
99 RIVET_DECLARE_PLUGIN(SND_2000_I527752);
100
101
102}
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