Rivet analyses

Mass and angular distributions in B⁺ → K⁺ηγ decays

Experiment: BELLE (KEKB)

Inspire ID: 1663447

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 97 (2018) 9, 092003

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+, originally Upsilno(4S) decay

Mass and angular distributions in B⁺ → K⁺ηγ decays. Data were read from the plots in the paper, but are background subtracted and efficiency corrected.

Source code:`BELLE_2018_I1663447.cc`

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

namespace Rivet {


  /// @brief B+ -> K+ eta gamma
  class BELLE_2018_I1663447 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2018_I1663447);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==521);
      declare(ufs, "UFS");
      DecayedParticles BP(ufs);
      BP.addStable(PID::ETA);
      declare(BP, "BP");
      for(unsigned int ix=0;ix<2;++ix)
    for(unsigned int iy=0;iy<2;++iy)
      book(_h[ix][iy],1+ix,1,1+iy);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 221,1},{ 321,1}, {22,1}};
      static const map<PdgId,unsigned int> & modeCC = { { 221,1},{-321,1}, {22,1}};
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      // loop over particles
      for(unsigned int ix=0;ix<BP.decaying().size();++ix) {
        int sign = 1;
        if (BP.decaying()[ix].pid()>0 && BP.modeMatches(ix,3,mode)) {
          sign=1;
        }
        else if  (BP.decaying()[ix].pid()<0 && BP.modeMatches(ix,3,modeCC)) {
          sign=-1;
        }
        else
          continue;
    const Particle & Kp    = BP.decayProducts()[ix].at( sign*321)[0];
    const Particle & eta   = BP.decayProducts()[ix].at(      221)[0];
    const Particle & gamma = BP.decayProducts()[ix].at(       22)[0];
    FourMomentum pKeta = Kp.momentum()+eta.momentum();
    double mass = pKeta.mass();
    LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(BP.decaying()[ix].momentum().betaVec());
    pKeta = boostB.transform(pKeta);
    LorentzTransform boostKeta = LorentzTransform::mkFrameTransformFromBeta(pKeta.betaVec());
    FourMomentum pK     = boostKeta.transform(boostB.transform(Kp   .momentum()));
    FourMomentum pGamma = boostB.transform(gamma.momentum());
    double cTheta = pK.p3().unit().dot(pGamma.p3().unit());
    for(unsigned int iy=0;iy<2;++iy) {
      _h[0][iy]->fill(cTheta);
      _h[1][iy]->fill(mass );
    }
      }
    }


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

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(BELLE_2018_I1663447);

}

Rivet analyses

Mass and angular distributions in B+ → K+ηγ decays

Source code:BELLE_2018_I1663447.cc

Mass and angular distributions in B⁺ → K⁺ηγ decays

Source code:`BELLE_2018_I1663447.cc`