1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/FinalState.hh"
  5#include "Rivet/Projections/UnstableParticles.hh"
  6
  7namespace Rivet {
  8
  9
 10  /// @brief Jpsi/psi2S baryon decay analysis
 11  class BESIII_2017_I1510563 : public Analysis {
 12  public:
 13
 14    /// Constructor
 15    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1510563);
 16
 17
 18    /// @name Analysis methods
 19    /// @{
 20
 21    /// Book histograms and initialise projections before the run
 22    void init() {
 23
 24      // Initialise and register projections
 25      declare(Beam(), "Beams");
 26      declare(UnstableParticles(), "UFS");
 27      declare(FinalState(), "FS");
 28
 29      // Book histograms
 30      if(isCompatibleWithSqrtS(3.1*GeV,1e-1)) {
 31        book(_h_lam, 1, 1, 1);
 32        book(_h_sig, 1, 1, 3);
 33      }
 34      else if (isCompatibleWithSqrtS(3.686*GeV, 1E-1)) {
 35        book(_h_lam, 1, 1, 2);
 36        book(_h_sig, 1, 1, 4);
 37      }
 38    }
 39
 40    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 41      for( const Particle &child : p.children()) {
 42        if(child.children().empty()) {
 43          nRes[child.pid()]-=1;
 44          --ncount;
 45        }
 46        else
 47          findChildren(child,nRes,ncount);
 48      }
 49    }
 50
 51    /// Perform the per-event analysis
 52    void analyze(const Event& event) {
 53      // get the axis, direction of incoming electron
 54      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
 55      Vector3 axis;
 56      if(beams.first.pid()>0)
 57        axis = beams.first .momentum().p3().unit();
 58      else
 59        axis = beams.second.momentum().p3().unit();
 60      // types of final state particles
 61      const FinalState& fs = apply<FinalState>(event, "FS");
 62      map<long,int> nCount;
 63      int ntotal(0);
 64      for (const Particle& p :  fs.particles()) {
 65        nCount[p.pid()] += 1;
 66        ++ntotal;
 67      }
 68      // loop over lambda0 and sigma0 baryons
 69      const UnstableParticles & ufs = apply<UnstableParticles>(event, "UFS");
 70      for (const Particle& p :  ufs.particles(Cuts::abspid==3122 or Cuts::abspid==3212)) {
 71        if(p.children().empty()) continue;
 72        map<long,int> nRes=nCount;
 73        int ncount = ntotal;
 74        findChildren(p,nRes,ncount);
 75        bool matched=false;
 76        // check for antiparticle
 77        for (const Particle& p2 :  ufs.particles(Cuts::pid==-p.pid())) {
 78          if(p2.children().empty()) continue;
 79          map<long,int> nRes2=nRes;
 80          int ncount2 = ncount;
 81          findChildren(p2,nRes2,ncount2);
 82          if(ncount2==0) {
 83            matched = true;
 84            for(auto const & val : nRes2) {
 85              if(val.second!=0) {
 86                matched = false;
 87                break;
 88              }
 89            }
 90            // fond baryon and antibaryon
 91            if(matched) {
 92              // calc cosine
 93              double ctheta;
 94              if(p.pid()>0)
 95                ctheta = p .momentum().p3().unit().dot(axis);
 96              else
 97                ctheta = p2.momentum().p3().unit().dot(axis);
 98              if(abs(p.pid())==3122)
 99                _h_lam->fill(ctheta);
100              else
101                _h_sig->fill(ctheta);
102              break;
103            }
104          }
105        }
106        if(matched) break;
107      }
108    }
109
110    pair<double,pair<double,double> > calcAlpha(Histo1DPtr hist) {
111      if(hist->numEntries()==0.) return make_pair(0.,make_pair(0.,0.));
112      double sum1(0.),sum2(0.),sum3(0.),sum4(0.),sum5(0.);
113      for (const auto& bin : hist->bins() ) {
114        double Oi = bin.sumW();
115        if(Oi==0.) continue;
116        double a =  1.5*(bin.xMax() - bin.xMin());
117        double b = 0.5*(pow(bin.xMax(),3) - pow(bin.xMin(),3));
118        double Ei = bin.errW();
119        sum1 +=   a*Oi/sqr(Ei);
120        sum2 +=   b*Oi/sqr(Ei);
121        sum3 += sqr(a)/sqr(Ei);
122        sum4 += sqr(b)/sqr(Ei);
123        sum5 +=    a*b/sqr(Ei);
124      }
125      // calculate alpha
126      double alpha = (-3*sum1 + 9*sum2 + sum3 - 3*sum5)/(sum1 - 3*sum2 + 3*sum4 - sum5);
127      // and error
128      double cc = -pow((sum3 + 9*sum4 - 6*sum5),3);
129      double bb = -2*sqr(sum3 + 9*sum4 - 6*sum5)*(sum1 - 3*sum2 + 3*sum4 - sum5);
130      double aa =  sqr(sum1 - 3*sum2 + 3*sum4 - sum5)*(-sum3 - 9*sum4 + sqr(sum1 - 3*sum2 + 3*sum4 - sum5) + 6*sum5);
131      double dis = sqr(bb)-4.*aa*cc;
132      if(dis>0.) {
133        dis = sqrt(dis);
134        return make_pair(alpha,make_pair(0.5*(-bb+dis)/aa,-0.5*(-bb-dis)/aa));
135      }
136      else {
137        return make_pair(alpha,make_pair(0.,0.));
138      }
139    }
140
141    /// Normalise histograms etc., after the run
142    void finalize() {
143      // find energy
144      int ioff=-1;
145      if (isCompatibleWithSqrtS(3.1*GeV,1e-1)) ioff=0;
146      else if (isCompatibleWithSqrtS(3.686*GeV, 1E-1))  ioff=1;
147      // normalize
148      normalize(_h_lam);
149      pair<double,pair<double,double> > alpha = calcAlpha(_h_lam);
150      Estimate1DPtr _h_alpha_lam;
151      book(_h_alpha_lam, 2,2*ioff+1,1);
152      _h_alpha_lam->bin(1).set(alpha.first, alpha.second);
153      normalize(_h_sig);
154      alpha = calcAlpha(_h_sig);
155      Estimate1DPtr _h_alpha_sig;
156      book(_h_alpha_sig, 2,2*ioff+2,1);
157      _h_alpha_sig->bin(1).set(alpha.first, alpha.second);
158    }
159
160    /// @}
161
162
163    /// @name Histograms
164    /// @{
165    Histo1DPtr _h_lam,_h_sig;
166    /// @}
167
168
169  };
170
171
172
173  RIVET_DECLARE_PLUGIN(BESIII_2017_I1510563);
174
175}