Rivet analyses

Mass and helicity angle distributions in B → ηK*

Experiment: BABAR (PEP-II)

Inspire ID: 722820

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 201802

Beams: * *

Beam energies: ANY

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

Measurement of the Kπ mass and helicity angle in B → ηK* decays. The data were read from Figure 2 in the paper and the backgrounds given subtracted.

Source code:BABAR_2006_I722820.cc

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

namespace Rivet {


  /// @brief B -> eta K*
  class BABAR_2006_I722820 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I722820);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projection
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(PID::ETA);
      BB.addStable(PID::K0S);
      BB.addStable(PID::PI0);
      declare(BB, "BB");
      // histograms
      for (unsigned int ix = 0; ix < 2; ++ix)
        for (unsigned int iy = 0; iy < 2; ++iy) book(_h[ix][iy], 1, 1 + ix, 1 + iy);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{321, 1}, {-211, 1}, {221, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{-321, 1}, {211, 1}, {221, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{321, 1}, {111, 1}, {221, 1}};
      static const map<PdgId, unsigned int>& mode2CC = {{-321, 1}, {111, 1}, {221, 1}};
      static const map<PdgId, unsigned int>& mode3 = {{310, 1}, {211, 1}, {221, 1}};
      static const map<PdgId, unsigned int>& mode3CC = {{310, 1}, {-211, 1}, {221, 1}};
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      // loop over particles
      for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
        int imode = 1, iK = 321, iPi = -211;
        if (BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode1)) {
          imode = 0;
          iK = 321;
          iPi = -211;
        }
        else if (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode1CC)) {
          imode = 0;
          iK = -321;
          iPi = 211;
        }
        else if (BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode2)) {
          iK = 321;
          iPi = 111;
        }
        else if (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode2CC)) {
          iK = -321;
          iPi = 111;
        }
        else if (BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode3)) {
          iK = 310;
          iPi = 211;
        }
        else if (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode3CC)) {
          iK = 310;
          iPi = -211;
        }
        else
          continue;
        const Particle& KK = BB.decayProducts()[ix].at(iK)[0];
        const Particle& pi = BB.decayProducts()[ix].at(iPi)[0];
        double mKpi = (KK.momentum() + pi.momentum()).mass();
        _h[0][imode]->fill(mKpi);
        // boost to b rest frame
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
            BB.decaying()[ix].momentum().betaVec());
        FourMomentum pK = boost1.transform(KK.momentum());
        FourMomentum ppi = boost1.transform(pi.momentum());
        FourMomentum pKS = pK + ppi;
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKS.betaVec());
        Vector3 axis = pKS.p3().unit();
        _h[1][imode]->fill(axis.dot(boost2.transform(pK).p3().unit()));
      }
    }


    /// 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(BABAR_2006_I722820);

}