Rivet analyses

Kinematic distributions in Ds+ → K+K−e+νe

Experiment: BABAR (PEP-II)

Inspire ID: 790461

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 78 (2008) 051101

Beams: * *

Beam energies: ANY

Run details: - Any process producing DS

Measurement of the kinematic distributions in Ds+ → K+K−e+νe by BaBar. N.B. the plots where read from the paper and may not have been corrected for acceptance.

Source code:BABAR_2008_I790461.cc

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

namespace Rivet {


  /// @brief D_s+ -> K+K- e+ nu_e
  class BABAR_2008_I790461 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I790461);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid==431);
      declare(ufs, "UFS");
      DecayedParticles DS(ufs);
      DS.addStable(PID::PI0);
      DS.addStable(PID::K0S);
      DS.addStable(PID::ETA);
      DS.addStable(PID::ETAPRIME);
      declare(DS, "DS");
      
      // Book histograms
      book(_h[0],1,1,1);
      for(unsigned int ix=0;ix<4;++ix)
    book(_h[ix+1],2,1,1+ix);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode = { { 321,1}, {-321,1}, {-11,1}, { 12,1}};
      DecayedParticles DS = apply<DecayedParticles>(event, "DS");
      // loop over particles
      for(unsigned int ix=0;ix<DS.decaying().size();++ix) {
    if(!DS.modeMatches(ix,4,mode)) continue;
    const Particle & Kp = DS.decayProducts()[ix].at( 321)[0];
    const Particle & Km = DS.decayProducts()[ix].at(-321)[0];
    const Particle & ep = DS.decayProducts()[ix].at( -11)[0];
    const Particle & nue= DS.decayProducts()[ix].at(  12)[0];
    FourMomentum pPhi = Kp.momentum()+Km.momentum(); 
    _h[0]->fill(pPhi.mass());
    FourMomentum qq = DS.decaying()[ix].momentum()-pPhi;
    _h[1]->fill(qq.mass2());
    // boost momenta to DS rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(DS.decaying()[ix].momentum().betaVec());
    FourMomentum pPHI = boost.transform(pPhi);
    Matrix3 ptoz(-pPHI.p3().unit(), Vector3(0,0,1));
    boost.preMult(ptoz);
    // the momenta in frane to W along z
    FourMomentum pD  = boost.transform(DS.decaying()[ix].momentum());
    FourMomentum pKp = boost.transform(Kp .momentum());
    FourMomentum pKm = boost.transform(Km .momentum());
    FourMomentum pe  = boost.transform(ep .momentum());
    FourMomentum pnu = boost.transform(nue.momentum());
    pPhi = pKp+pKm;
    qq = pD-pPhi;
    LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
    Vector3 axisK = boostK.transform(pKp).p3().unit();
    _h[3]->fill(axisK.dot(pPhi.p3().unit()));
    LorentzTransform boostW = LorentzTransform::mkFrameTransformFromBeta(  qq.betaVec());
    Vector3 axisE = boostW.transform(pe).p3().unit();
    _h[2]->fill(axisE.dot(qq.p3().unit()));
    axisK.setZ(0.);
    axisE.setZ(0.);
    double chi = atan2(axisE.cross(axisK).dot(qq.p3().unit()), axisE.dot(axisK));
    _h[4]->fill(chi);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<5;++ix)
    normalize(_h[ix]);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[5];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2008_I790461);

}