1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4#include "Rivet/Projections/DecayedParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief Bbar0 -> D0 pi+ pi-
 10  class BELLE_2007_I733011 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I733011);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // projections
 23      UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
 24      declare(ufs, "UFS");
 25      DecayedParticles B0(ufs);
 26      B0.addStable( 421);
 27      B0.addStable(-421);
 28      declare(B0, "B0");
 29      // histos
 30      for(unsigned int ix=0;ix<3;++ix) {
 31      	book(_h_pipi[ix], 3,1,1+ix);
 32      	if (ix==2) continue;
 33      	book(_h_mass[ix], 1,1,1+ix);
 34      	book(_h_Dpi [ix], 2,1,1+ix);
 35      }
 36    }
 37
 38
 39    /// Perform the per-event analysis
 40    void analyze(const Event& event) {
 41      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
 42      for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
 43      	int sign = 1;
 44      	if (B0.decaying()[ix].pid()>0 && B0.modeMatches(ix,3,mode))        sign= 1;
 45      	else if (B0.decaying()[ix].pid()<0 && B0.modeMatches(ix,3,modeCC)) sign=-1;
 46        else {
 47          continue;
 48        }
 49        const Particle& pip = B0.decayProducts()[ix].at( sign*211)[0];
 50        const Particle& pim = B0.decayProducts()[ix].at(-sign*211)[0];
 51        const Particle& D0  = B0.decayProducts()[ix].at(-sign*421)[0];
 52        // compute the helicity angles
 53        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix].mom().betaVec());
 54        // D pi mass and angle
 55        FourMomentum pDpi = D0.mom()+pim.mom();
 56        double mDpi = pDpi.mass();
 57        pDpi = boost1.transform(pDpi);
 58        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDpi.betaVec());
 59        FourMomentum pD = boost2.transform(boost1.transform(D0.mom()));
 60        double cDpi = pD.p3().unit().dot(pDpi.p3().unit());
 61        // fill histos
 62        if      (abs(mDpi-2.46)<.1) _h_Dpi[0]->fill(cDpi);
 63        else if (abs(mDpi-2.30)<.1) _h_Dpi[1]->fill(cDpi);
 64        if (cDpi>0.) _h_mass[0]->fill(mDpi);
 65        // pi pi mass and angle
 66        FourMomentum ppipi = pim.mom()+pip.mom();
 67        double mpipi = ppipi.mass();
 68        ppipi = boost1.transform(ppipi);
 69        LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
 70        FourMomentum ppip = boost3.transform(boost1.transform(pip.mom()));
 71        double cpipi = -ppip.p3().unit().dot(ppipi.p3().unit());
 72        // fill angles
 73        if      (abs(mpipi-0.78)<0.2) _h_pipi[0]->fill(cpipi);
 74        else if (abs(mpipi-1.20)<0.1) _h_pipi[1]->fill(cpipi);
 75        else if (mpipi<0.6)           _h_pipi[2]->fill(cpipi);
 76        if (cpipi>0.) _h_mass[1]->fill(mpipi);
 77      }
 78    }
 79
 80
 81    /// Normalise histograms etc., after the run
 82    void finalize() {
 83      normalize(_h_pipi, 1.0, false);
 84      normalize(_h_mass, 1.0, false);
 85      normalize(_h_Dpi,  1.0, false);
 86    }
 87
 88    /// @}
 89
 90
 91    /// @name Histograms
 92    /// @{
 93    Histo1DPtr _h_mass[2],_h_Dpi[2],_h_pipi[3];
 94    const map<PdgId,unsigned int> mode   = { { 211,1}, {-211,1}, {-421,1}};
 95    const map<PdgId,unsigned int> modeCC = { { 211,1}, {-211,1}, { 421,1}};
 96    /// @}
 97
 98
 99      };
100
101
102  RIVET_DECLARE_PLUGIN(BELLE_2007_I733011);
103
104}