1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief J/psi production at low energies
 9  class BESIII_2021_I1908066 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1908066);
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(UnstableParticles(), "UFS");
24      book(_c_psi   , "/TMP/sigma_psi");
25    }
26
27
28    /// Perform the per-event analysis
29    void analyze(const Event& event) {
30      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
31      unsigned int count = ufs.particles(Cuts::pid==443).size();
32      _c_psi->fill(count);
33    }
34
35
36    /// Normalise histograms etc., after the run
37    void finalize() {
38      double fact = crossSection()/nanobarn/sumOfWeights();
39      double sigma = _c_psi->val()*fact;
40      double error = _c_psi->err()*fact;
41      Scatter2D temphisto(refData(1, 1, 1));
42      Scatter2DPtr mult;
43      book(mult, 1, 1, 1);
44      for (size_t b = 0; b < temphisto.numPoints(); b++) {
45	const double x  = temphisto.point(b).x();
46	pair<double,double> ex = temphisto.point(b).xErrs();
47	pair<double,double> ex2 = ex;
48	if(ex2.first ==0.) ex2. first=0.0001;
49	if(ex2.second==0.) ex2.second=0.0001;
50	if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
51	  mult   ->addPoint(x, sigma, ex, make_pair(error,error));
52	}
53	else {
54	  mult   ->addPoint(x, 0., ex, make_pair(0.,.0));
55	}
56      }
57    }
58
59    ///@}
60
61
62    /// @name Histograms
63    ///@{
64    CounterPtr _c_psi;
65    ///@}
66
67
68  };
69
70
71  RIVET_DECLARE_PLUGIN(BESIII_2021_I1908066);
72
73}