Rivet analyses referenceBESIII_2020_I1814783$e^+e^-\to\Sigma^+\bar{\Sigma}^-$ and $\Sigma^-\bar{\Sigma}^+$ cross sections for centre-of-mass energies between 2.3864 and 3 GeVExperiment: BESIII (BEPC) Inspire ID: 1814783 Status: VALIDATED Authors:
Beam energies: ANY Run details:
$e^+e^-\to\Sigma^+\bar{\Sigma}^-$ and $\Sigma^-\bar{\Sigma}^+$ cross sections for centre-of-mass energies between 2.3864 and 3 GeV. The angular distribution for $\sqrt{s}=2.396$\,GeV is also measured. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: BESIII_2020_I1814783.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- > sigma+- sigmabar -+
10 class BESIII_2020_I1814783 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1814783);
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 book(_n_plus ,"/TMP/NPLUS" );
26 book(_n_minus,"/TMP/NMINUS");
27 if(isCompatibleWithSqrtS(2.396, 1E-2)) {
28 book(_h_cTheta_A,3,1,1);
29 book(_h_cTheta_B,3,1,2);
30 }
31 }
32
33 void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
34 for(const Particle &child : p.children()) {
35 if(child.children().empty()) {
36 nRes[child.pid()]-=1;
37 --ncount;
38 }
39 else
40 findChildren(child,nRes,ncount);
41 }
42 }
43
44 /// Perform the per-event analysis
45 void analyze(const Event& event) {
46 const FinalState& fs = apply<FinalState>(event, "FS");
47 // total hadronic and muonic cross sections
48 map<long,int> nCount;
49 int ntotal(0);
50 for (const Particle& p : fs.particles()) {
51 nCount[p.pid()] += 1;
52 ++ntotal;
53 }
54 // find the Sigmas
55 const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
56 for(unsigned int ix=0;ix<ufs.particles().size();++ix) {
57 const Particle& p1 = ufs.particles()[ix];
58 if(abs(p1.pid())!=3112&&abs(p1.pid())!=3222) continue;
59 bool matched = false;
60 // check fs
61 bool fs = true;
62 for(const Particle & child : p1.children()) {
63 if(child.pid()==p1.pid()) {
64 fs = false;
65 break;
66 }
67 }
68 if(!fs) continue;
69 // find the children
70 map<long,int> nRes = nCount;
71 int ncount = ntotal;
72 findChildren(p1,nRes,ncount);
73 for(unsigned int iy=ix+1;iy<ufs.particles().size();++iy) {
74 const Particle& p2 = ufs.particles()[iy];
75 if(p2.pid() != -p1.pid()) continue;
76 // check fs
77 bool fs = true;
78 for(const Particle & child : p2.children()) {
79 if(child.pid()==p2.pid()) {
80 fs = false;
81 break;
82 }
83 }
84 if(!fs) continue;
85 map<long,int> nRes2 = nRes;
86 int ncount2 = ncount;
87 findChildren(p2,nRes2,ncount2);
88 if(ncount2!=0) continue;
89 matched=true;
90 for(auto const & val : nRes2) {
91 if(val.second!=0) {
92 matched = false;
93 break;
94 }
95 }
96 if(matched) {
97 if(abs(p1.pid())==3222) {
98 _n_plus->fill();
99 if(_h_cTheta_A) {
100 double cTheta = p1.pid()>0 ?
101 cos(p1.momentum().polarAngle()) :
102 cos(p2.momentum().polarAngle());
103 _h_cTheta_A->fill(cTheta);
104 _h_cTheta_B->fill(cTheta);
105 }
106 }
107 else if(abs(p1.pid())==3112)
108 _n_minus->fill();
109 break;
110 }
111 }
112 if(matched) break;
113 }
114
115 }
116
117
118 /// Normalise histograms etc., after the run
119 void finalize() {
120 if(_h_cTheta_A) {
121 normalize(_h_cTheta_A);
122 normalize(_h_cTheta_B);
123 }
124 double fact = crossSection()/ sumOfWeights() /picobarn;
125 for(unsigned int iy=1;iy<3;++iy) {
126 double sigma,error;
127 if(iy==1) {
128 sigma = _n_plus->val()*fact;
129 error = _n_plus->err()*fact;
130 }
131 else {
132 sigma = _n_minus->val()*fact;
133 error = _n_minus->err()*fact;
134 }
135 for(unsigned int ix=1;ix<3;++ix) {
136 Scatter2D temphisto(refData(ix, 1, iy));
137 Scatter2DPtr mult;
138 book(mult, ix, 1, iy);
139 for (size_t b = 0; b < temphisto.numPoints(); b++) {
140 const double x = temphisto.point(b).x();
141 pair<double,double> ex = temphisto.point(b).xErrs();
142 pair<double,double> ex2 = ex;
143 if(ex2.first ==0.) ex2. first=0.0001;
144 if(ex2.second==0.) ex2.second=0.0001;
145 if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
146 mult->addPoint(x, sigma, ex, make_pair(error,error));
147 }
148 else {
149 mult->addPoint(x, 0., ex, make_pair(0.,.0));
150 }
151 }
152 }
153 }
154 }
155 ///@}
156
157
158 /// @name Histograms
159 ///@{
160 CounterPtr _n_plus,_n_minus;
161 Histo1DPtr _h_cTheta_A,_h_cTheta_B;
162 ///@}
163
164
165 };
166
167
168 RIVET_DECLARE_PLUGIN(BESIII_2020_I1814783);
169
170}
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