Rivet analyses

Helicity angle in B⁰ → D^∓K^*±

Experiment: BABAR (PEP-II)

Inspire ID: 667017

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 95 (2005) 171802

Beams: * *

Beam energies: ANY

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

Measurement of the helicity angle in B⁰ → D^∓K^*± decays. The efficiency corrected, background subtracted decay were read from figure 3 in the paper.

Source code:`BABAR_2005_I667017.cc`

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

namespace Rivet {


  /// @brief B0 -> D-+ K*+-
  class BABAR_2005_I667017 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I667017);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projection
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
      declare(ufs, "UFS");
      // hists
      book(_h,1,1,1);
    }

    bool isK(int pid) const {
      return pid==130 || pid==310 || pid==311 || pid==321;
    }

    bool isPi(int pid) const {
      return pid==211 || pid==111;
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      UnstableParticles ufs = apply<UnstableParticles>(event, "UFS");
      for(const Particle & B : ufs.particles()) {
        if(B.children().size()!=2) continue;
        int sign = B.pid()/B.abspid();
        Particle Kstar;
        if(B.children()[0].pid()==-sign*411 &&
           B.children()[1].pid()== sign*323) {
      Kstar = B.children()[1];
    }
    else if(B.children()[1].pid()==-sign*411 &&
        B.children()[0].pid()== sign*323) {
      Kstar = B.children()[0];
    }
    else
      continue;
        // find Kstar decay products
        Particle KK;
        if(isK (Kstar.children()[0].abspid()) &&
           isPi(Kstar.children()[1].abspid())) {
          KK = Kstar.children()[0];
        }
        else if(isK (Kstar.children()[1].abspid()) &&
            isPi(Kstar.children()[0].abspid())) {
          KK = Kstar.children()[1];
        }
        else
          continue;
    // boost to B rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(B.momentum().betaVec());
    FourMomentum pKstar = boost.transform(Kstar.momentum());
    FourMomentum pK     = boost.transform(KK   .momentum());
    // kaon helicity angle
    Vector3 axisX = pKstar.p3().unit();
    LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
    double cosK =  axisX.dot(boostK.transform(pK).p3().unit());
        _h->fill(cosK);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h,1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2005_I667017);

}

Rivet analyses

Helicity angle in B0 → D∓K*±

Source code:BABAR_2005_I667017.cc

Helicity angle in B⁰ → D^∓K^*±

Source code:`BABAR_2005_I667017.cc`