1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/ChargedFinalState.hh"
  5#include "Rivet/Projections/UnstableParticles.hh"
  6
  7namespace Rivet {
  8
  9
 10  /// @brief  e+e- > tau+ tau-
 11  class OPAL_2001_I554583 : public Analysis {
 12  public:
 13
 14    /// Constructor
 15    RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2001_I554583);
 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      declare(Beam(), "Beams");
 25      declare(ChargedFinalState(), "FS");
 26      declare(UnstableParticles(), "UFS");
 27      // book histos
 28      const vector<double> edges{-0.9, -0.72, -0.54, -0.36, -0.18, 0., 0.18, 0.36, 0.54, 0.72, 0.9};
 29      book(_h_e, edges);
 30      book(_h_mu, edges);
 31      book(_h_pi, edges);
 32      book(_h_rho, edges);
 33      for (size_t ix=0; ix<_h_e->numBins(); ++ix) {
 34        const string suff = std::to_string(ix);
 35        book(_h_e->bin(ix+1), "_h_e_"+suff, 20, -1.0, 1.0);
 36        book(_h_mu->bin(ix+1), "_h_mu_"+suff, 20, -1.0, 1.0);
 37        book(_h_pi->bin(ix+1), "_h_pi_"+suff, 20, -1.0, 1.0);
 38        book(_h_rho->bin(ix+1), "_h_rho_"+suff, 20, -1.0, 1.0);
 39      }
 40      book(_t_e  ,"_t_e " , 20,-1,1);
 41      book(_t_mu ,"_t_mu" , 20,-1,1);
 42      book(_t_pi ,"_t_pi" , 20,-1,1);
 43      book(_t_rho,"_t_rho", 20,-1,1);
 44    }
 45
 46    void findTau(const Particle & p, unsigned int & nprod, Particles& piP,
 47     		         Particles& pi0, Particles& ell, Particles& nu_ell, Particles& nu_tau) {
 48      for (const Particle & child : p.children()) {
 49        if(child.pid()==PID::ELECTRON || child.pid()==PID::MUON) {
 50          ++nprod;
 51          ell.push_back(child);
 52        }
 53        else if(child.pid()==PID::NU_EBAR || child.pid()==PID::NU_MUBAR) {
 54          ++nprod;
 55          nu_ell.push_back(child);
 56        }
 57        else if(child.pid()==PID::PIMINUS) {
 58          ++nprod;
 59          piP.push_back(child);
 60        }
 61        else if(child.pid()==PID::PI0) {
 62          ++nprod;
 63          pi0.push_back(child);
 64        }
 65        else if(child.pid()==PID::NU_TAU) {
 66          ++nprod;
 67          nu_tau.push_back(child);
 68        }
 69        else if(child.pid()==PID::GAMMA) {
 70          continue;
 71        }
 72        else if(child.children().empty() || child.pid()==221 || child.pid()==331) {
 73          ++nprod;
 74        }
 75        else {
 76          findTau(child,nprod,piP,pi0,ell,nu_ell,nu_tau);
 77        }
 78      }
 79    }
 80
 81    /// Perform the per-event analysis
 82    void analyze(const Event& event) {
 83      // require 2 chanrged particles to veto hadronic events
 84      if(apply<ChargedFinalState>(event, "FS").particles().size()!=2) vetoEvent;
 85      // Get beams and average beam momentum
 86      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
 87      Vector3 axis;
 88      if (beams.first.pid()>0) {
 89        axis = beams.first .momentum().p3().unit();
 90      }
 91      else {
 92        axis = beams.second.momentum().p3().unit();
 93      }
 94      // loop over tau leptons
 95      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==15)) {
 96        unsigned int nprod(0);
 97        Particles piP, pi0, ell, nu_ell, nu_tau;
 98        findTau(p,nprod,piP, pi0, ell, nu_ell, nu_tau);
 99        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
100        double cBeam = axis.dot(p.momentum().p3().unit());
101        if (nprod==2 && nu_tau.size()==1 && piP.size()==1) {
102          FourMomentum pPi = boost1.transform(piP[0].momentum());
103          double cTheta = pPi.p3().unit().dot(p.momentum().p3().unit());
104          _h_pi->fill(cBeam, cTheta);
105          _t_pi->fill(cTheta);
106        }
107        else if (nprod==3 && nu_tau.size()==1 && ell.size()==1 && nu_ell.size()==1) {
108          if (ell[0].pid()==PID::ELECTRON) {
109            _h_e->fill(cBeam,2.*ell[0].momentum().t()/sqrtS());
110            _t_e ->fill(2.*ell[0].momentum().t()/sqrtS());
111          }
112          else {
113            _h_mu->fill(cBeam,2.*ell[0].momentum().t()/sqrtS());
114            _t_mu->fill(2.*ell[0].momentum().t()/sqrtS());
115          }
116        }
117        else if(nprod==3 && nu_tau.size()==1 && piP.size()==1&& pi0.size()==1) {
118          FourMomentum pRho = boost1.transform(piP[0].momentum()+pi0[0].momentum());
119          double cTheta = pRho.p3().unit().dot(p.momentum().p3().unit());
120          _h_rho->fill(cBeam, cTheta);
121          _t_rho->fill(cTheta);
122        }
123      }
124    }
125
126    pair<double,double> calcP(Histo1DPtr hist,unsigned int imode) {
127      if(hist->numEntries()==0.) return make_pair(0.,0.);
128      double sum1(0.),sum2(0.);
129      for (const auto& bin : hist->bins() ) {
130        double Oi = bin.sumW();
131        if(Oi==0.) continue;
132        double ai(0.),bi(0.);
133        // tau -> pi/rho nu
134        if(imode==0) {
135          ai = 0.5*(bin.xMax()-bin.xMin());
136          bi = 0.5*ai*(bin.xMax()+bin.xMin());
137        }
138        // lepton mode
139        else {
140          ai = (-5*bin.xMin() + 3*pow(bin.xMin(),3) -   pow(bin.xMin(),4) + 5*bin.xMax() - 3*pow(bin.xMax(),3) +   pow(bin.xMax(),4))/3.;
141          bi = (  -bin.xMin() + 3*pow(bin.xMin(),3) - 2*pow(bin.xMin(),4) +   bin.xMax() - 3*pow(bin.xMax(),3) + 2*pow(bin.xMax(),4))/3.;
142        }
143        double Ei = bin.errW();
144        sum1 += sqr(bi/Ei);
145        sum2 += bi/sqr(Ei)*(Oi-ai);
146      }
147      return make_pair(sum2/sum1,sqrt(1./sum1));
148    }
149
150    /// Normalise histograms etc., after the run
151    void finalize() {
152      Estimate1DPtr _h_P;
153      book(_h_P,2,1,1);
154      BinnedEstimatePtr<string> _t_P;
155      book(_t_P,1,1,5);
156      for (size_t ix=0; ix < _h_e->numBins()+1; ++ix) {
157        Histo1DPtr& he = ix<10 ? _h_e->bin(ix+1) : _t_e;
158      	normalize(he);
159       	pair<double,double> P_e  = calcP(he, 1);
160       	double s1 = P_e.first/sqr(P_e.second);
161       	double s2 = 1./sqr(P_e.second);
162        Histo1DPtr& hmu = ix<10 ? _h_mu->bin(ix+1) : _t_mu;
163      	normalize(hmu);
164      	pair<double,double> P_mu = calcP(hmu,1);
165      	s1 += P_mu.first/sqr(P_mu.second);
166      	s2 += 1./sqr(P_mu.second);
167        Histo1DPtr& hpi = ix<10 ? _h_pi->bin(ix+1) : _t_pi;
168      	normalize(hpi);
169        pair<double,double> P_pi = calcP(hpi,0);
170        s1 += P_pi.first/sqr(P_pi.second);
171        s2 += 1./sqr(P_pi.second);
172        Histo1DPtr& hrho = ix<10 ? _h_rho->bin(ix+1) : _t_rho;
173      	normalize(hrho);
174      	pair<double,double> P_rho = calcP(hrho,0);
175	P_rho.first  /=0.46;
176	P_rho.second /=0.46;
177      	s1 += P_rho.first/sqr(P_rho.second);
178      	s2 += 1./sqr(P_rho.second);
179       	// average
180        if(ix<10)
181          _h_P->bin(ix+1).set(s1/s2, sqrt(1./s2));
182        else
183	  _t_P->bin(1).set(s1/s2,sqrt(1./s2));
184      }
185    }
186
187    /// @}
188
189
190    /// @name Histograms
191    /// @{
192    Histo1DGroupPtr _h_e,_h_mu,_h_pi,_h_rho;
193    Histo1DPtr      _t_e,_t_mu,_t_pi,_t_rho;
194    /// @}
195
196
197  };
198
199
200  RIVET_DECLARE_PLUGIN(OPAL_2001_I554583);
201
202}