1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Cross section for $e^+e^-\to p \bar{p} \pi^0$ at energies between 4.008 and 4.600 GeV
 9  class BESIII_2017_I1509241 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1509241);
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 histograms
26      book(_nproton, "TMP/proton");
27
28    }
29
30
31    /// Perform the per-event analysis
32    void analyze(const Event& event) {
33      const FinalState& fs = apply<FinalState>(event, "FS");
34      if(fs.particles().size()!=3) vetoEvent;
35      for (const Particle& p :  fs.particles()) {
36        if(abs(p.pid())!=PID::PROTON&& p.pid()==PID::PI0) vetoEvent;
37      }
38      _nproton->fill();
39    }
40
41
42    /// Normalise histograms etc., after the run
43    void finalize() {
44      double sigma = _nproton->val();
45      double error = _nproton->err();
46      sigma *= crossSection()/ sumOfWeights() /picobarn;
47      error *= crossSection()/ sumOfWeights() /picobarn;
48      Estimate1D temphisto(refData(1, 1, 1));
49      Estimate1DPtr  mult;
50      book(mult, 1, 1, 1);
51      for (auto& b : mult->bins()) {
52        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
53          b.set(sigma, error);
54        }
55      }
56    }
57
58    /// @}
59
60
61    /// @name Histograms
62    /// @{
63    CounterPtr _nproton;
64    /// @}
65
66
67  };
68
69
70  RIVET_DECLARE_PLUGIN(BESIII_2017_I1509241);
71
72}