Rivet analyses

B⁰ → η^′K^*0 decays

Experiment: BABAR (PEP-II)

Inspire ID: 722710

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 98 (2007) 051802

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0, originally Upsilon(4S) decay

Measurement of the K^*0 mass and helicity angle distributions for B⁰ → η^′K^*0 by Babar. The data was read from the plots in the paper which are however background subtracted and efficiency corrected.

Source code:`BABAR_2007_I722710.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief  B0 -> K*0 eta' 
  class BABAR_2007_I722710 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I722710);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // projection
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(PID::ETAPRIME);
      declare(B0, "B0");
      // histograms
      for(unsigned int ix=0;ix<2;++ix)
    book(_h[ix],ix+1,1,1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 321,1},{-211,1}, { 331,1}};
      static const map<PdgId,unsigned int> & modeCC = { {-321,1},{ 211,1}, { 331,1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
        int sign = 1;
        if (B0.decaying()[ix].pid()>0 && B0.modeMatches(ix,3,mode)) {
          sign=1;
        }
        else if  (B0.decaying()[ix].pid()<0 && B0.modeMatches(ix,3,modeCC)) {
          sign=-1;
        }
        else
          continue;
    const Particle & Kp  = B0.decayProducts()[ix].at( sign*321)[0];
    const Particle & pim = B0.decayProducts()[ix].at(-sign*211)[0];
    double mKpi  = (Kp.momentum()+pim.momentum()).mass();
    if(mKpi<.755 || mKpi>1.305) continue;
    _h[0]->fill(mKpi);
    // boost to b rest frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix].momentum().betaVec());
    FourMomentum pK  = boost1.transform(Kp.momentum());
    FourMomentum ppi = boost1.transform(pim.momentum());
    FourMomentum pKS = pK+ppi;
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKS.betaVec());
    Vector3 axis = pKS.p3().unit();
    _h[1]->fill(axis.dot(boost2.transform(pK).p3().unit()));
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<2;++ix)
    normalize(_h[ix],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2007_I722710);

}

Rivet analyses

B0 → η′K*0 decays

Source code:BABAR_2007_I722710.cc

B⁰ → η^′K^*0 decays

Source code:`BABAR_2007_I722710.cc`