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-> n nbar
10  class FENICE_1998_I471263 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(FENICE_1998_I471263);
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(_nNeutron, 1,1,1);
26      for (const string& en : _nNeutron.binning().edges<0>()) {
27        const double end = std::stod(en)*GeV;
28        if (isCompatibleWithSqrtS(end)) {
29          _ecms = en;
30          break;
31        }
32      }
33      if (_ecms.empty())
34        MSG_ERROR("Beam energy incompatible with analysis.");
35    }
36
37
38    /// Perform the per-event analysis
39    void analyze(const Event& event) {
40      const FinalState& fs = apply<FinalState>(event, "FS");
41      // total hadronic and muonic cross sections
42      map<long,int> nCount;
43      int ntotal(0);
44      for (const Particle& p : fs.particles()) {
45	nCount[p.pid()] += 1;
46	++ntotal;
47      }
48      if(ntotal==2 && nCount[2112]==1 && nCount[-2112]==1)
49	_nNeutron->fill(_ecms);
50    }
51
52
53    /// Normalise histograms etc., after the run
54    void finalize() {
55      scale(_nNeutron, crossSection()/ sumOfWeights() /nanobarn);
56    }
57
58    /// @}
59
60
61    /// @name Histograms
62    /// @{
63    BinnedHistoPtr<string> _nNeutron;
64    string _ecms;
65    /// @}
66
67
68  };
69
70
71  RIVET_DECLARE_PLUGIN(FENICE_1998_I471263);
72
73
74}