1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief gamma gamma -> pi+pi-/K+ K-
 9  class MARKII_1984_I195739 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1984_I195739);
14
15
16    /// @name Analysis methods
17    ///@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      declare(FinalState(),"FS");
22      // check CMS energy in range
23      if (sqrtS()<1.6*GeV || sqrtS()>2.5*GeV)
24        throw Error("Invalid CMS energy for MARKII_1984_I195739");
25      book(_cPiK, "/TMP/nPiK_");
26    }
27
28
29    /// Perform the per-event analysis
30    void analyze(const Event& event) {
31      Particles part = apply<FinalState>(event,"FS").particles();
32      if (part.size()!=2) vetoEvent;
33      if (part[0].pid()!=-part[1].pid()) vetoEvent;
34      double cTheta(0.);
35      bool foundPi(false),foundK(false);
36      for (const Particle& p : part) {
37        if (p.pid()==PID::PIPLUS) {
38          foundPi=true;
39          cTheta = abs(p.momentum().z()/p.momentum().p3().mod());
40        }
41        else if (p.pid()==PID::KPLUS) {
42          foundK=true;
43          cTheta = abs(p.momentum().z()/p.momentum().p3().mod());
44        }
45      }
46      if (!foundPi && !foundK) vetoEvent;
47      if (cTheta>0.3) vetoEvent;
48      _cPiK->fill();
49    }
50
51
52    /// Normalise histograms etc., after the run
53    void finalize() {
54      double fact = crossSection()/nanobarn/sumOfWeights();
55      double sigma = _cPiK->val()*fact;
56      double error = _cPiK->err()*fact;
57      Estimate1DPtr cross;
58      book(cross, 1, 1, 1);
59      for (auto& b : cross->bins()) {
60        if (inRange(sqrtS(), b.xMin(), b.xMax())) {
61          b.set(sigma, error);
62        }
63      }
64    }
65
66    ///@}
67
68
69    /// @name Histograms
70    ///@{
71    CounterPtr _cPiK;
72    ///@}
73
74
75  };
76
77
78  RIVET_DECLARE_PLUGIN(MARKII_1984_I195739);
79
80}