Rivet analyses

B̄0 → D*+ωπ− decays

Experiment: BABAR (PEP-II)

Inspire ID: 713862

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 74 (2006) 012001

Beams: * *

Beam energies: ANY

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

Measurement of mass distributions and the D*+ polarization in B̄0 → D*+ωπ− decays. The background subtracted/corrected data for the mass distributions was read from the figures in the paper and the polarization from Table 1.

Source code:BABAR_2006_I713862.cc

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

namespace Rivet {


  /// @brief Bbar0 -> D*+ omega pi-
  class BABAR_2006_I713862 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I713862);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(PID::PI0);
      BB.addStable(413);
      BB.addStable(-413);
      BB.addStable(223);
      declare(BB, "BB");
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1 + ix, 1, 1);
      book(_p, 3, 1, 1);
      book(_c, "TMP/nB");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{-413, 1}, {211, 1}, {223, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{413, 1}, {-211, 1}, {223, 1}};
      // loop over particles
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
        _c->fill();
        int sign = BB.decaying()[ix].pid() / BB.decaying()[ix].abspid();
        if ((sign == 1 && BB.modeMatches(ix, 3, mode1)) || (sign == -1 && BB.modeMatches(ix, 3, mode1CC))) {
          const Particle& omega = BB.decayProducts()[ix].at(223)[0];
          const Particle& pim = BB.decayProducts()[ix].at(sign * 211)[0];
          const Particle& Dstar = BB.decayProducts()[ix].at(-sign * 413)[0];
          double mX = (omega.momentum() + pim.momentum()).mass();
          _h[0]->fill(sqr(mX));
          if (Dstar.children().size() != 2) continue;
          // boost to B rest frame
          LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
              BB.decaying()[ix].momentum().betaVec());
          FourMomentum pDpi = boost1.transform(Dstar.momentum() + pim.momentum());
          LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDpi.betaVec());
          FourMomentum pDstar = boost2.transform(boost1.transform(Dstar.momentum()));
          double c1 = pDstar.p3().unit().dot(pDpi.p3().unit());
          if (c1 < 0.5) _h[1]->fill(pDpi.mass());
          Particle D0;
          if (Dstar.children()[0].pid() == -sign * 211 && Dstar.children()[1].abspid() == -sign * 421)
            D0 = Dstar.children()[1];
          else if (Dstar.children()[1].pid() == -sign * 211 && Dstar.children()[0].abspid() == -sign * 421)
            D0 = Dstar.children()[0];
          else
            continue;
          FourMomentum pD0 = boost2.transform(boost1.transform(D0.momentum()));
          LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pDstar.betaVec());
          pD0 = boost3.transform(pD0);
          double cTheta = pD0.p3().unit().dot(pDstar.p3().unit());
          _p->fill(mX, .5 * (5. * sqr(cTheta) - 1.));
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // first hist is differential BR/ BR for leptons
      double br = .1033;
      scale(_h[0], 1. / br / *_c);
      normalize(_h[1], 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2];
    Profile1DPtr _p;
    CounterPtr _c;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2006_I713862);

}