Rivet analyses referenceBESIII_2021_I1933191Cross section for $e^+e^-\to \psi(2S)\pi^+\pi^-$ at energies between 4.0 and 4.7 GeVExperiment: BESIII (BEPC) Inspire ID: 1933191 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the cross section for $e^+e^-\to \psi(2S)\pi^+\pi^-$ at energies between 4.0 and 4.7 GeV by the BES collaboration. Source code: BESIII_2021_I1933191.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- > psi(2S) pi+pi-
10 class BESIII_2021_I1933191 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1933191);
15
16
17 /// @name Analysis methods
18 ///@{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 declare(FinalState(), "FS");
23 declare(UnstableParticles(), "UFS");
24 book(_nPsi2s, "TMP/psi2s");
25 }
26
27 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
28 for (const Particle &child : p.children()) {
29 if(child.children().empty()) {
30 --nRes[child.pid()];
31 --ncount;
32 }
33 else
34 findChildren(child,nRes,ncount);
35 }
36 }
37
38
39 /// Perform the per-event analysis
40 void analyze(const Event& event) {
41 const FinalState& fs = apply<FinalState>(event, "FS");
42 map<long,int> nCount;
43 int ntotal(0);
44 for (const Particle& p : fs.particles()) {
45 nCount[p.pid()] += 1;
46 ++ntotal;
47 }
48 const FinalState& ufs = apply<FinalState>(event, "UFS");
49 for (const Particle& p : ufs.particles()) {
50 if(p.children().empty()) continue;
51 // find the psi(2S)
52 if(p.pid()==100443) {
53 map<long,int> nRes = nCount;
54 int ncount = ntotal;
55 findChildren(p,nRes,ncount);
56 // omega pi+pi-
57 if(ncount!=2) continue;
58 bool matched = true;
59 for(auto const & val : nRes) {
60 if(abs(val.first)==211) {
61 if(val.second !=1) {
62 matched = false;
63 break;
64 }
65 }
66 else if(val.second!=0) {
67 matched = false;
68 break;
69 }
70 }
71 if(matched) {
72 _nPsi2s->fill();
73 break;
74 }
75 }
76 }
77 }
78
79
80 /// Normalise histograms etc., after the run
81 void finalize() {
82 double sigma = _nPsi2s->val();
83 double error = _nPsi2s->err();
84 sigma *= crossSection()/ sumOfWeights() /picobarn;
85 error *= crossSection()/ sumOfWeights() /picobarn;
86 Estimate1DPtr mult;
87 book(mult, 1, 1, 3);
88 for (auto& b : mult->bins()) {
89 if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
90 b.set(sigma, error);
91 }
92 }
93 }
94
95 ///@}
96
97
98 /// @name Histograms
99 ///@{
100 CounterPtr _nPsi2s;
101 ///@}
102
103
104 };
105
106
107 RIVET_DECLARE_PLUGIN(BESIII_2021_I1933191);
108
109}
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