Rivet analyses

B⁰ → η^′K^*0 decays

Experiment: BABAR (PEP-II)

Inspire ID: 722710

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 98 (2007) 051802

Beams: * *

Beam energies: ANY

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

Measurement of the K^*0 mass and helicity angle distributions for B⁰ → η^′K^*0 by Babar. The data was read from the plots in the paper which are however background subtracted and efficiency corrected.

Source code:`BABAR_2007_I722710.cc`

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

namespace Rivet {


  /// @brief  B0 -> K*0 eta'
  class BABAR_2007_I722710 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I722710);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projection
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(PID::ETAPRIME);
      declare(B0, "B0");
      // histograms
      for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], ix + 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{321, 1}, {-211, 1}, {331, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {211, 1}, {331, 1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
        int sign = 1;
        if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode)) {
          sign = 1;
        }
        else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, modeCC)) {
          sign = -1;
        }
        else
          continue;
        const Particle& Kp = B0.decayProducts()[ix].at(sign * 321)[0];
        const Particle& pim = B0.decayProducts()[ix].at(-sign * 211)[0];
        double mKpi = (Kp.momentum() + pim.momentum()).mass();
        if (mKpi < .755 || mKpi > 1.305) continue;
        _h[0]->fill(mKpi);
        // boost to b rest frame
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
            B0.decaying()[ix].momentum().betaVec());
        FourMomentum pK = boost1.transform(Kp.momentum());
        FourMomentum ppi = boost1.transform(pim.momentum());
        FourMomentum pKS = pK + ppi;
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKS.betaVec());
        Vector3 axis = pKS.p3().unit();
        _h[1]->fill(axis.dot(boost2.transform(pK).p3().unit()));
      }
    }


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

    /// @}


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


  RIVET_DECLARE_PLUGIN(BABAR_2007_I722710);

}

Rivet analyses

B0 → η′K*0 decays

Source code:BABAR_2007_I722710.cc

B⁰ → η^′K^*0 decays

Source code:`BABAR_2007_I722710.cc`