1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief gamma gamma -> pi+pi-
 9  class VENUS_1995_I392360 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(VENUS_1995_I392360);
14
15
16    /// @name Analysis methods
17    ///@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // Final state
22      declare(FinalState(),"FS");
23      // check CMS energy in range
24      if (!inRange(sqrtS(), 1*GeV, 1.5*GeV)) {
25        throw Error("Invalid CMS energy for VENUS_1995_I392360");
26      }
27      // bin for the angle plots
28      int ibin = (sqrtS()-1.0)/0.05 + 2;
29      book(_h_cTheta, ibin, 1, 1);
30      book(_cPi, 1, 1, 1);
31      _cmax = ibin>2 ? 0.6 : 0.4;
32      if (ibin == 2)  _axis = YODA::Axis<double>(4, 0.0, 0.4);
33      else            _axis = YODA::Axis<double>(6, 0.0, 0.6);
34      _ecms = _cPi.binning().edges<0>()[ibin-2];
35    }
36
37
38    /// Perform the per-event analysis
39    void analyze(const Event& event) {
40      if (_edges.empty())  _edges = _h_cTheta->xEdges();
41      Particles part = apply<FinalState>(event, "FS").particles();
42      if (part.size()!=2) vetoEvent;
43      double cTheta(0.);
44      bool foundP(false),foundM(false);
45      for (const Particle& p : part) {
46        if (p.pid()==PID::PIPLUS) {
47          foundP = true;
48          cTheta = abs(p.momentum().z()/p.momentum().p3().mod());
49        }
50        else if (p.pid()==PID::PIMINUS)
51          foundM = true;
52      }
53      if (!foundP || !foundM) vetoEvent;
54      if (cTheta<=_cmax)    _cPi->fill(_ecms);
55      if (_h_cTheta )  _h_cTheta->fill(map2string(cTheta));
56    }
57
58    string map2string(const double value) const {
59      const size_t idx = _axis.index(value) - 1;
60      if (idx < _edges.size())  return _edges[idx];
61      return "OTHER";
62    }
63
64    /// Normalise histograms etc., after the run
65    void finalize() {
66      const double fact = crossSection()/nanobarn/sumOfWeights();
67      if (_h_cTheta ) {
68        scale(_h_cTheta, fact);
69        for(auto & b : _h_cTheta->bins()) {
70          const size_t idx = b.index();
71          b.scaleW(1./_axis.width(idx));
72        }
73      }
74      scale(_cPi, fact);
75    }
76
77    ///@}
78
79
80    /// @name Histograms
81    ///@{
82    BinnedHistoPtr<string> _h_cTheta,_cPi;
83    double _cmax;
84    YODA::Axis<double> _axis;
85    vector<string> _edges;
86    string _ecms;
87    ///@}
88
89
90  };
91
92
93  RIVET_DECLARE_PLUGIN(VENUS_1995_I392360);
94
95}