1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4
  5namespace Rivet {
  6
  7
  8  /// @brief B -> pi, eta and omega decays
  9  class BABAR_2012_I1125973 : public Analysis {
 10  public:
 11
 12    /// Constructor
 13    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1125973);
 14
 15
 16    /// @name Analysis methods
 17    /// @{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21
 22      // Initialise and register projections
 23      declare(UnstableParticles(Cuts::pid==PID::BPLUS || Cuts::pid==PID::B0), "UFS");
 24
 25      // histograms
 26      for(unsigned int ix=0;ix<2;++ix) {
 27	book(_h_B0_pi[ix], 1, 1, ix+1);
 28	book(_h_Bp_pi[ix], 2, 1, ix+1);
 29	book(_nB[ix],"TMP/nB_"+toString(ix+1));
 30      }
 31      book(_h_omega,3,1,1);
 32      book(_h_eta  ,4,1,1);
 33    }
 34
 35    // Calculate the Q2 using mother and daughter charged lepton
 36    double q2(const Particle& B, int mesonID) {
 37      FourMomentum q = B.mom() - select(B.children(), Cuts::pid==mesonID)[0];
 38      return q*q;
 39    }
 40
 41    // Check for explicit decay into pdgids
 42    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
 43      // Trivial check to ignore any other decays but the one in question modulo photons
 44      const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
 45      if (children.size()!=ids.size()) return false;
 46      // Check for the explicit decay
 47      return all(ids, [&](int i){return count(children, hasPID(i))==1;});
 48    }
 49
 50    /// Perform the per-event analysis
 51    void analyze(const Event& event) {
 52      // Get B+ Mesons
 53      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
 54	if( p.pid()==PID::B0) {
 55	  _nB[0]->fill();
 56	  if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E}) ||
 57	      isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
 58	    double Q2 = q2(p,PID::PIMINUS);
 59            _h_B0_pi[0]->fill(Q2);
 60            _h_B0_pi[1]->fill(Q2);
 61	  }
 62	}
 63	else {
 64	  _nB[1]->fill();
 65	  if (isSemileptonicDecay(p, {PID::PI0, PID::POSITRON, PID::NU_E}) ||
 66	      isSemileptonicDecay(p, {PID::PI0, PID::ANTIMUON, PID::NU_MU})) {
 67	    double Q2 = q2(p,PID::PI0);
 68            _h_Bp_pi[0]->fill(Q2);
 69            _h_Bp_pi[1]->fill(Q2);
 70	  }
 71	  else if (isSemileptonicDecay(p, {PID::OMEGA, PID::POSITRON, PID::NU_E}) ||
 72		   isSemileptonicDecay(p, {PID::OMEGA, PID::ANTIMUON, PID::NU_MU})) {
 73	    _h_omega->fill(q2(p,PID::OMEGA));
 74	  }
 75	  else if (isSemileptonicDecay(p, {PID::ETA, PID::POSITRON, PID::NU_E}) ||
 76		   isSemileptonicDecay(p, {PID::ETA, PID::ANTIMUON, PID::NU_MU})) {
 77            _h_eta->fill(q2(p,PID::ETA));
 78	  }
 79	}
 80      }
 81    }
 82
 83
 84    /// Normalise histograms etc., after the run
 85    void finalize() {
 86      // BR in units of 10^{-7}
 87      for(unsigned int ix=0;ix<2;++ix) {
 88	scale(_h_B0_pi[ix], 1e7/ *_nB[0]);
 89	scale(_h_Bp_pi[ix], 1e7/ *_nB[1]);
 90      }
 91      scale(_h_omega,1e7/ *_nB[1]);
 92      scale(_h_eta  ,1e7/ *_nB[1]);
 93    }
 94
 95    /// @}
 96
 97
 98    /// @name Histograms
 99    /// @{
100    CounterPtr _nB[2];
101    Histo1DPtr _h_B0_pi[2],_h_Bp_pi[2],_h_omega,_h_eta;
102    /// @}
103
104
105  };
106
107
108  RIVET_DECLARE_PLUGIN(BABAR_2012_I1125973);
109
110}