Rivet analyses referenceBELLE_2018_I1672149$\gamma\gamma\to\eta^\prime\pi^+\pi^-$ for centre-of-mass energies between 1.4 and 3.8 GeVExperiment: BELLE (KEKB) Inspire ID: 1672149 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the cross section for $\gamma\gamma\to\eta^\prime\pi^+\pi^-$ for centre-of-mass energies between 1.4 and 3.8 GeV. The resonance subprocess $\gamma\gamma\to f_2(1270)\eta^\prime$ is alos measured, and subtracted from the final result above 2.26 GeV. The contribution from $\eta_c(1)$ is also subtracted between 2.62,3.06 GeV. Source code: BELLE_2018_I1672149.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 gamma gamma -> eta' pi+pi-
10 class BELLE_2018_I1672149 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2018_I1672149);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // Initialise and register projections
23 declare(FinalState(), "FS");
24 declare(UnstableParticles(), "UFS");
25 // counters
26 for (unsigned int ix=0; ix<2; ++ix) {
27 book(_sigma[ix],"TMP/sigma_"+toString(ix+1),refData(1+ix,1,1));
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 }
42
43 /// Perform the per-event analysis
44 void analyze(const Event& event) {
45 const FinalState& fs = apply<FinalState>(event, "FS");
46 // find the final-state particles
47 map<long,int> nCount;
48 int ntotal(0);
49 for (const Particle& p : fs.particles()) {
50 nCount[p.pid()] += 1;
51 ++ntotal;
52 }
53 const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
54 // first check for f_2 eta'
55 bool foundf2(false);
56 Particles f2s = ufs.particles(Cuts::pid==225);
57 Particles etaps = ufs.particles(Cuts::pid==331);
58 for (const Particle & f2 : f2s) {
59 bool matched=false;
60 map<long,int> nRes=nCount;
61 int ncount = ntotal;
62 findChildren(f2,nRes,ncount);
63 for (const Particle & etap : etaps) {
64 map<long,int> nRes2=nRes;
65 int ncount2 = ncount;
66 findChildren(etap,nRes2,ncount2);
67 if (ncount2 !=0 ) continue;
68 matched = true;
69 for (const auto& val : nRes2) {
70 if (val.second!=0) {
71 matched = false;
72 break;
73 }
74 }
75 if (matched) {
76 foundf2 = true;
77 break;
78 }
79 }
80 if (foundf2) break;
81 }
82 // if we have the f_2 eta' state
83 if (foundf2) {
84 _sigma[0]->fill(sqrtS());
85 if (sqrtS()>2.26*GeV) vetoEvent;
86 }
87 // see if we have eta' pi+pi-
88 bool foundetap(false);
89 for (const Particle & etap : etaps) {
90 bool matched=false;
91 map<long,int> nRes=nCount;
92 int ncount = ntotal;
93 findChildren(etap,nRes,ncount);
94 if (ncount !=2 ) continue;
95 matched=true;
96 for (const auto& val : nRes) {
97 if (abs(val.first)==211) {
98 if (val.second!=1) {
99 matched = false;
100 break;
101 }
102 }
103 else if (val.second!=0) {
104 matched = false;
105 break;
106 }
107 }
108 if (matched) {
109 foundetap = true;
110 break;
111 }
112 }
113 // check there's no eta_c
114 if (foundetap && sqrtS()>2.62 && sqrtS()<3.06) {
115 for (const Particle& etac : ufs.particles(Cuts::pid==441)) {
116 bool matched=false;
117 map<long,int> nRes=nCount;
118 int ncount = ntotal;
119 findChildren(etac,nRes,ncount);
120 for(const auto& val : nRes) {
121 if (val.second!=0) {
122 matched = false;
123 break;
124 }
125 }
126 if (matched) {
127 foundetap=false;
128 break;
129 }
130 }
131 }
132 if (foundetap) _sigma[1]->fill(sqrtS());
133 }
134
135 /// Normalise histograms etc., after the run
136 void finalize() {
137 const double fact = crossSection()/nanobarn/sumOfWeights();
138 // loop over tables in paper
139 for(unsigned int ix=0;ix<2;++ix) {
140 scale(_sigma[ix],fact);
141 Estimate1DPtr tmp;
142 book(tmp, ix+1, 1, 1);
143 barchart(_sigma[ix],tmp);
144 }
145 }
146
147 /// @}
148
149
150 /// @name Histograms
151 /// @{
152 Histo1DPtr _sigma[2];
153 /// @}
154
155
156 };
157
158
159 RIVET_DECLARE_PLUGIN(BELLE_2018_I1672149);
160
161}
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