1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5#include "Rivet/Projections/DecayedParticles.hh"
  6
  7namespace Rivet {
  8
  9
 10  /// @brief J/psi -> gamma omega omega
 11  class BESII_2006_I715175 : public Analysis {
 12  public:
 13
 14    /// Constructor
 15    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2006_I715175);
 16
 17
 18    /// @name Analysis methods
 19    /// @{
 20
 21    /// Book histograms and initialise projections before the run
 22    void init() {
 23      // Initialise and register projections
 24      UnstableParticles ufs = UnstableParticles(Cuts::abspid==443);
 25      declare(ufs, "UFS");
 26      DecayedParticles PSI(ufs);
 27      PSI.addStable(PID::OMEGA);
 28      declare(PSI, "PSI");
 29      declare(Beam(), "Beams");
 30      // histos
 31      for (unsigned int ix=0; ix<6; ++ix) {
 32        book(_h[ix], 1, 1, 1+ix);
 33      }
 34    }
 35
 36    // angle cuts due regions of BES calorimeter
 37    bool vetoPhoton(const double& cTheta) {
 38      return cTheta>0.92 || (cTheta>0.8 && cTheta<0.86);
 39    }
 40
 41    void findChildren(const Particle& p, Particles& pim, Particles& pip,
 42                      Particles& pi0, unsigned int &ncount) {
 43      for (const Particle& child : p.children()) {
 44        if (child.pid()==PID::PIPLUS) {
 45          pip.push_back(child);
 46          ncount+=1;
 47        }
 48        else if (child.pid()==PID::PIMINUS) {
 49          pim.push_back(child);
 50          ncount+=1;
 51        }
 52        else if (child.pid()==PID::PI0) {
 53          pi0.push_back(child);
 54          ncount+=1;
 55        }
 56        else if (child.children().empty()) {
 57          ncount+=1;
 58        }
 59        else {
 60          findChildren(child,pim,pip,pi0,ncount);
 61        }
 62      }
 63    }
 64
 65    /// Perform the per-event analysis
 66    void analyze(const Event& event) {
 67      Vector3 trans[2];
 68      // get the axis, direction of incoming electron
 69      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
 70      Vector3 axis;
 71      if (beams.first.pid()>0) {
 72        axis = beams.first .mom().p3().unit();
 73      }
 74      else {
 75        axis = beams.second.mom().p3().unit();
 76      }
 77      // find the J/psi decays
 78      DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
 79      if ( PSI.decaying().size()!=1)  vetoEvent;
 80      if (!PSI.modeMatches(0,3,mode)) vetoEvent;
 81      // particles
 82      const Particles& omega = PSI.decayProducts()[0].at(223);
 83      const Particle & gam   = PSI.decayProducts()[0].at( 22)[0];
 84      // photon polar angle
 85      double cTheta = axis.dot(gam.p3().unit());
 86      if (vetoPhoton(abs(cTheta))) vetoEvent;
 87      // remaining angles
 88      LorentzTransform boost1  = LorentzTransform::mkFrameTransformFromBeta(PSI.decaying()[0].mom().betaVec());
 89      FourMomentum pGamma      = boost1.transform(gam.mom());
 90      FourMomentum pOmegaOmega = boost1.transform(omega[0].mom()+omega[1].mom());
 91      Vector3 e1z = pGamma.p3().unit();
 92      Vector3 e1y = e1z.cross(axis).unit();
 93      Vector3 e1x = e1y.cross(e1z).unit();
 94      LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pOmegaOmega.betaVec());
 95      Vector3 axis2 = boost2.transform(boost1.transform(omega[0].mom())).p3().unit();
 96      double cOmega[2], phiOmega[2], cN[2];
 97      for (unsigned int ix=0; ix<2; ++ix) {
 98        Vector3 axis3 = boost2.transform(boost1.transform(omega[ix].mom())).p3().unit();
 99        cOmega[ix] = e1z.dot(axis3) ;
100        phiOmega[ix] = atan2(axis3.dot(e1y),axis3.dot(e1x));
101        if (phiOmega[ix]<0.) phiOmega[ix]+=2.*M_PI;
102        // omega decay
103        unsigned int ncount=0;
104        Particles pip,pim,pi0;
105        findChildren(omega[ix],pim,pip,pi0,ncount);
106        if (ncount!=3 || !(pim.size()==1 && pip.size()==1 && pi0.size()==1)) vetoEvent;
107        FourMomentum ppip = boost2.transform(boost1.transform(pip[0].mom()));
108        FourMomentum ppim = boost2.transform(boost1.transform(pim[0].mom()));
109        FourMomentum pOmega = boost2.transform(boost1.transform(omega[ix].mom()));
110        LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pOmega.betaVec());
111        // boost to omega frame
112        Vector3 axisZ = pOmega.p3().unit();
113        ppip = boost3.transform(ppip);
114        ppim = boost3.transform(ppim);
115        Vector3 norm = ppip.p3().cross(ppim.p3()).unit();
116        cN[ix] = norm.dot(axisZ);
117        trans[ix] = norm - cN[ix]*axisZ;
118      }
119      // finally fill all the histos
120      // photon polar angle
121      _h[0]->fill(cTheta);
122      // azimuthal angle
123      _h[1]->fill(gam.p3().phi()/M_PI*180.);
124      // omega angles
125      for (unsigned int ix=0; ix<2; ++ix) {
126        _h[2]->fill(cOmega[ix]);
127        _h[3]->fill(180.*phiOmega[ix]/M_PI);
128        _h[4]->fill(cN[ix]);
129      }
130      const double chi = atan(trans[0].cross(trans[1]).dot(axis2)/trans[0].dot(trans[1]));
131      _h[5]->fill(abs(chi)/M_PI*180.);
132    }
133
134
135    /// Normalise histograms etc., after the run
136    void finalize() {
137      normalize(_h, 1.0, false);
138    }
139
140    /// @}
141
142
143    /// @name Histograms
144    /// @{
145    Histo1DPtr _h[6];
146    const map<PdgId,unsigned int> mode = { { 223,2},{ 22,1}};
147    /// @}
148
149
150  };
151
152
153  RIVET_DECLARE_PLUGIN(BESII_2006_I715175);
154
155}