Rivet analyses referenceBESIII_2019_I1773081$e^+e^-\to\pi^+\pi^-\pi^0$ cross section between 0.7 GeV to 3.0 GeVExperiment: BESIII (BEPC) Inspire ID: 1773081 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Cross section for $e^+e^-\to\pi^+\pi^-\pi^0$ cross section for centre-of-mass energies between 0.7 GeV to 3.0 GeV measured by the BES III experiment using radiative return. Source code: BESIII_2019_I1773081.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4
5namespace Rivet {
6
7
8 /// @brief e+e- to 3 pi from BES
9 class BESIII_2019_I1773081 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1773081);
14
15
16 /// @name Analysis methods
17 //@{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21
22 // Initialise and register projections
23 declare(FinalState(), "FS");
24
25 book(_num3pi, "TMP/num3");
26
27 }
28
29
30 /// Perform the per-event analysis
31 void analyze(const Event& event) {
32 const FinalState& fs = apply<FinalState>(event, "FS");
33
34 map<long,int> nCount;
35 int ntotal(0);
36 for (const Particle& p : fs.particles()) {
37 nCount[p.pid()] += 1;
38 ++ntotal;
39 }
40 if(ntotal!=3) vetoEvent;
41 if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==1)
42 _num3pi->fill();
43
44 }
45
46
47 /// Normalise histograms etc., after the run
48 void finalize() {
49
50 double sigma = _num3pi->val();
51 double error = _num3pi->err();
52 sigma *= crossSection()/ sumOfWeights() /nanobarn;
53 error *= crossSection()/ sumOfWeights() /nanobarn;
54 Scatter2D temphisto(refData(1, 1, 1));
55 Scatter2DPtr mult;
56 book(mult, 1, 1, 1);
57 for (size_t b = 0; b < temphisto.numPoints(); b++) {
58 const double x = temphisto.point(b).x();
59 pair<double,double> ex = temphisto.point(b).xErrs();
60 pair<double,double> ex2 = ex;
61 if(ex2.first ==0.) ex2. first=0.0001;
62 if(ex2.second==0.) ex2.second=0.0001;
63 if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
64 mult->addPoint(x, sigma, ex, make_pair(error,error));
65 }
66 else {
67 mult->addPoint(x, 0., ex, make_pair(0.,.0));
68 }
69 }
70 }
71
72 //@}
73
74
75 /// @name Histograms
76 //@{
77 CounterPtr _num3pi;
78 //@}
79
80
81 };
82
83
84 RIVET_DECLARE_PLUGIN(BESIII_2019_I1773081);
85
86}
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