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/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.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);

}