Rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

BELLE_2017_I1512299

Decay kinematics of semileptonc B0bar to D*+ decays.
Experiment: BELLE (KEKB)
Inspire ID: 1512299
Status: VALIDATED
Authors:
  • Holger Schulz
No references listed
Beams: * *
Beam energies: ANY
Run details:
  • Semileptonic B0bar (-511) decays.

Unfolded measurement of recoil w, helicity and decay plane angles of semileptonc B0bar to D*+ decays. The data was used to determine Vcb. Note that the data in the paper does not account for the bin wodths. The data shipped with rivet is divided by the bin width and all curves are normalised to the partial width of B0bar-> D*+ ell nu

Source code: BELLE_2017_I1512299.cc
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableFinalState.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class BELLE_2017_I1512299 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BELLE_2017_I1512299);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableFinalState(), "UFS");

      // Book histograms
      _h_w      = bookHisto1D(1, 1, 1);
      _h_costhv = bookHisto1D(2, 1, 1);
      _h_costhl = bookHisto1D(3, 1, 1);
      _h_chi    = bookHisto1D(4, 1, 1);

    }


    /// Perform the per-event analysis
    bool analyzeDecay(Particle mother, vector<int> ids) {
      // There is no point in looking for decays with less particles than to be analysed
      if (mother.children().size() == ids.size()) {
        bool decayfound = true;
        for (int id : ids) {
          if (!contains(mother, id)) decayfound = false;
        }
        return decayfound;
      }
      return false;
    }

    bool contains(Particle& mother, int id) {
      return any(mother.children(), HasPID(id));
    }


    double recoilW(const Particle& mother) {
      FourMomentum lepton, neutrino, meson, q;
      foreach(const Particle& c, mother.children()) {
        if (c.isNeutrino()) neutrino=c.mom();
        if (c.isLepton() &! c.isNeutrino()) lepton =c.mom();
        if (c.isHadron()) meson=c.mom();
      }
      q = lepton + neutrino; //no hadron before
      double mb2= mother.mom()*mother.mom();
      double mD2 = meson*meson;
      return (mb2 + mD2 - q*q )/ (2. * sqrt(mb2) * sqrt(mD2) );
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      FourMomentum pl, pnu, pB, pD, pDs, ppi;
      // Iterate of B0bar mesons
      for(const Particle& p : apply<UnstableFinalState>(event, "UFS").particles(Cuts::pid==-511)) {
        pB = p.momentum();
        // Find semileptonic decays
        if (analyzeDecay(p, {PID::DSTARPLUS,-12,11}) || analyzeDecay(p, {PID::DSTARPLUS,-14,13}) ) {
          _h_w->fill(recoilW(p), event.weight());
          // Get the necessary momenta for the angles
          bool foundDdecay=false;
          for (const Particle c : p.children()) {
            if ( (c.pid() == PID::DSTARPLUS)  && (analyzeDecay(c, {PID::PIPLUS, PID::D0}) || analyzeDecay(c, {PID::PI0, PID::DPLUS})) ) {
              foundDdecay=true;
              pDs = c.momentum();
              for (const Particle dc : c.children()) {
                if (dc.hasCharm()) pD = dc.momentum(); 
                else ppi = dc.momentum(); 
              }
            }
            if (c.pid() ==  11 || c.pid() ==  13) pl  = c.momentum();
            if (c.pid() == -12 || c.pid() == -14) pnu = c.momentum();
          }
          // This is the angle analysis
          if (foundDdecay) {

            // First boost all relevant momenta into the B-rest frame
            const LorentzTransform B_boost = LorentzTransform::mkFrameTransformFromBeta(pB.betaVec());
            // Momenta in B rest frame:
            FourMomentum lv_brest_Dstar = B_boost.transform(pDs);//lab2brest(gp_Dstar.particle.p());
            FourMomentum lv_brest_w     = B_boost.transform(pB - pDs); //lab2brest(p_lv_w);
            FourMomentum lv_brest_D     = B_boost.transform(pD); //lab2brest(gp_D.particle.p());
            FourMomentum lv_brest_lep   = B_boost.transform(pl); //lab2brest(gp_lep.p());
            
            const LorentzTransform Ds_boost = LorentzTransform::mkFrameTransformFromBeta(pDs.betaVec());
            FourMomentum lv_Dstarrest_D     = Ds_boost.transform(lv_brest_D);
            const LorentzTransform W_boost  = LorentzTransform::mkFrameTransformFromBeta((pB-pDs).betaVec());
            FourMomentum lv_wrest_lep       = W_boost.transform(lv_brest_lep);

            double cos_thetaV = cos(lv_brest_Dstar.p3().angle(lv_Dstarrest_D.p3()));
            _h_costhv->fill(cos_thetaV, event.weight());
            
            double cos_thetaL = cos(lv_brest_w.p3().angle(lv_wrest_lep.p3()));
            _h_costhl->fill(cos_thetaL, event.weight());

            Vector3 LTrans = lv_wrest_lep.p3()   - cos_thetaL*lv_wrest_lep.p3().perp()*lv_brest_w.p3().unit();
            Vector3 VTrans = lv_Dstarrest_D.p3() - cos_thetaV*lv_Dstarrest_D.p3().perp()*lv_brest_Dstar.p3().unit();
            float chi = atan2(LTrans.cross(VTrans).dot(lv_brest_w.p3().unit()), LTrans.dot(VTrans));
            if(chi < 0) chi += TWOPI; 

            _h_chi->fill(chi, event.weight());

            //const LorentzTransform W_boost = LorentzTransform::mkFrameTransformFromBeta((pl+pnu).betaVec());
            //const LorentzTransform D_boost = LorentzTransform::mkFrameTransformFromBeta((pD+ppi).betaVec());

            //FourMomentum pl_t = FourMomentum(W_boost.transform(pl));
            //FourMomentum pD_t = FourMomentum(D_boost.transform(pD));
            //double thetal = (pl+pnu).angle(pl_t);
            //double thetav = (pD+ppi).angle(pD_t);
            //_h_costhv->fill(cos(thetav), event.weight());
            //_h_costhl->fill(cos(thetal), event.weight());
          }
        }
      }
    }
        //else if (analyzeDecay(p, {413,-14,13}) ) {
          //_h_w->fill(recoilW(p), event.weight());
        //}

    /// Normalise histograms etc., after the run
    void finalize() {
    
      double GAMMA_B0 = 4.32e-13; // Total width in GeV, calculated from mean life time of 1.52 pico seconds
      double BR_B0_DSPLUS_ELL_NU = 0.0495; // Branching fraction from the same paper for B0bar to D*+ ell nu
      double NORM = GAMMA_B0 * BR_B0_DSPLUS_ELL_NU; // Normalise histos to partial width
      normalize(_h_w,      NORM); 
      normalize(_h_costhv, NORM); 
      normalize(_h_costhl, NORM); 
      normalize(_h_chi,    NORM);
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_w;
    Histo1DPtr _h_costhv;
    Histo1DPtr _h_costhl;
    Histo1DPtr _h_chi;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BELLE_2017_I1512299);


}