1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/ChargedFinalState.hh"
 4#include "Rivet/Projections/FinalState.hh"
 5
 6namespace Rivet {
 7
 8
 9  class CMS_2012_I1193338 : public Analysis {
10  public:
11
12    CMS_2012_I1193338()
13      : Analysis("CMS_2012_I1193338")
14    {    }
15
16
17    void init() {
18      declare(ChargedFinalState((Cuts::etaIn(-2.4, 2.4) && Cuts::pT >=  0.2*GeV)), "CFS");
19      declare(FinalState(), "FS");
20
21      book(_h_sigma ,1, 1, 1);
22    }
23
24
25    void analyze(const Event& event) {
26      const double weight = 1.0;
27
28      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
29      if (cfs.size() > 1) {_h_sigma->fill(1.5, weight);}
30      if (cfs.size() > 2) {_h_sigma->fill(2.5, weight);}
31      if (cfs.size() > 3) {_h_sigma->fill(3.5, weight);}
32
33      const FinalState& fs = apply<FinalState>(event, "FS");
34      if (fs.size() < 2) vetoEvent; // need at least two particles to calculate gaps
35
36      double gapcenter = 0.;
37      double LRG = 0.;
38      double etapre = 0.;
39      bool first = true;
40
41      for(const Particle& p : fs.particles(cmpMomByEta)) { // sorted from minus to plus
42        if (first) { // First particle
43          first = false;
44          etapre = p.eta();
45        } else {
46          double gap = fabs(p.eta()-etapre);
47          if (gap > LRG) {
48            LRG = gap; // largest gap
49            gapcenter = (p.eta()+etapre)/2.; // find the center of the gap to separate the X and Y systems.
50          }
51          etapre = p.eta();
52        }
53      }
54
55
56      FourMomentum mxFourVector, myFourVector;
57      for(const Particle& p : fs.particles(cmpMomByEta)) {
58        ((p.eta() > gapcenter) ? mxFourVector : myFourVector) += p.momentum();
59      }
60      const double M2 = max(mxFourVector.mass2(), myFourVector.mass2());
61      const double xi = M2/sqr(sqrtS()); // sqrt(s)=7000 GeV, note that units cancel
62      if (xi < 5e-6) vetoEvent;
63
64      _h_sigma->fill(0.5, weight);
65    }
66
67
68    void finalize() {
69      scale(_h_sigma, crossSection()/millibarn/sumOfWeights());
70    }
71
72  private:
73
74    Histo1DPtr _h_sigma;
75
76  };
77
78
79  // The hook for the plugin system
80  RIVET_DECLARE_PLUGIN(CMS_2012_I1193338);
81
82}