1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/IdentifiedFinalState.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// D0 direct photon pair production
 10  class D0_2010_I846997 : public Analysis {
 11  public:
 12
 13    RIVET_DEFAULT_ANALYSIS_CTOR(D0_2010_I846997);
 14
 15
 16    void init() {
 17      FinalState fs;
 18      declare(fs, "FS");
 19
 20      IdentifiedFinalState ifs(Cuts::abseta < 0.9 && Cuts::pT > 20*GeV);
 21      ifs.acceptId(PID::PHOTON);
 22      declare(ifs, "IFS");
 23
 24      book(_h_M ,1, 1, 1);
 25      book(_h_pT ,2, 1, 1);
 26      book(_h_dPhi ,3, 1, 1);
 27      book(_h_costheta ,4, 1, 1);
 28
 29      book(_h_pT_M, {30., 50., 80., 350.}, {"d05-x01-y01", "d08-x01-y01", "d11-x01-y01"});
 30      book(_h_dPhi_M, {30., 50., 80., 350.}, {"d06-x01-y01", "d09-x01-y01", "d12-x01-y01"});
 31      book(_h_costheta_M, {30., 50., 80., 350.}, {"d07-x01-y01", "d10-x01-y01", "d13-x01-y01"});
 32    }
 33
 34
 35    /// Perform the per-event analysis
 36    void analyze(const Event& event) {
 37
 38      Particles photons = apply<IdentifiedFinalState>(event, "IFS").particlesByPt();
 39      if (photons.size() < 2 ||
 40          (photons[0].pT() < 21.0*GeV)) {
 41        vetoEvent;
 42      }
 43
 44      // Isolate photons with ET_sum in cone
 45      Particles isolated_photons;
 46      Particles fs = apply<FinalState>(event, "FS").particles();
 47      for (const Particle& photon : photons) {
 48        double eta_P = photon.eta();
 49        double phi_P = photon.phi();
 50        double Etsum=0.0;
 51        for (const Particle& p : fs) {
 52          if (HepMCUtils::uniqueId(p.genParticle()) != HepMCUtils::uniqueId(photon.genParticle()) &&
 53              deltaR(eta_P, phi_P, p.eta(), p.phi()) < 0.4) {
 54            Etsum += p.Et();
 55          }
 56        }
 57        if (Etsum < 2.5*GeV) {
 58          isolated_photons.push_back(photon);
 59        }
 60      }
 61
 62      if (isolated_photons.size() != 2) {
 63        vetoEvent;
 64      }
 65      std::sort(isolated_photons.begin(), isolated_photons.end(), cmpMomByPt);
 66
 67      FourMomentum y1=isolated_photons[0].momentum();
 68      FourMomentum y2=isolated_photons[1].momentum();
 69      if (deltaR(y1, y2)<0.4)  vetoEvent;
 70
 71      FourMomentum yy=y1+y2;
 72      double Myy = yy.mass()/GeV;
 73      if (Myy<30.0 || Myy>350.0)  vetoEvent;
 74
 75      double pTyy = yy.pT()/GeV;
 76      if (Myy<pTyy)  vetoEvent;
 77
 78      double dPhiyy = mapAngle0ToPi(y1.phi()-y2.phi());
 79      if (dPhiyy<0.5*M_PI)  vetoEvent;
 80
 81      double costhetayy = fabs(tanh((y1.eta()-y2.eta())/2.0));
 82
 83      _h_M->fill(Myy);
 84      _h_pT->fill(pTyy);
 85      _h_dPhi->fill(dPhiyy);
 86      _h_costheta->fill(costhetayy);
 87
 88      _h_pT_M->fill(Myy, pTyy);
 89      _h_dPhi_M->fill(Myy, dPhiyy);
 90      _h_costheta_M->fill(Myy, costhetayy);
 91    }
 92
 93
 94    void finalize() {
 95
 96      scale(_h_M, crossSection()/picobarn/sumOfWeights());
 97      scale(_h_pT, crossSection()/picobarn/sumOfWeights());
 98      scale(_h_dPhi, crossSection()/picobarn/sumOfWeights());
 99      scale(_h_costheta, crossSection()/picobarn/sumOfWeights());
100
101      scale(_h_pT_M, crossSection()/picobarn/sumOfWeights());
102      scale(_h_dPhi_M, crossSection()/picobarn/sumOfWeights());
103      scale(_h_costheta_M, crossSection()/picobarn/sumOfWeights());
104
105      divByGroupWidth({_h_pT_M, _h_dPhi_M, _h_costheta_M});
106    }
107
108
109  private:
110
111    Histo1DPtr _h_M;
112    Histo1DPtr _h_pT;
113    Histo1DPtr _h_dPhi;
114    Histo1DPtr _h_costheta;
115    Histo1DGroupPtr _h_pT_M, _h_dPhi_M, _h_costheta_M;
116
117  };
118
119
120
121  RIVET_DECLARE_ALIASED_PLUGIN(D0_2010_I846997, D0_2010_S8570965);
122
123}