Rivet analyses

Helicity angle in B → Ds1+(2460)D̄ decays

Experiment: BABAR (PEP-II)

Inspire ID: 656424

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 242001

Beams: * *

Beam energies: ANY

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

Helicity angle in B → Ds1+(2460)D̄ decays. The efficiency corrected, background subtracted data was read from Figure 3 in the paper.

Source code:BABAR_2004_I656424.cc

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

namespace Rivet {


  /// @brief B -> Ds1(2460) Dbar
  class BABAR_2004_I656424 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2004_I656424);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
      declare(ufs, "UFS");
      // histos
      book(_h, 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      Particles BB = apply<UnstableParticles>(event, "UFS").particles();
      for (const Particle& p : BB) {
        if (p.children().size() != 2) continue;
        int sign = p.pid() / p.abspid();
        int iD = -sign * (p.abspid() - 100);
        Particle Ds1;
        if (p.children()[0].pid() == sign * 20433 && p.children()[1].pid() == iD) {
          Ds1 = p.children()[0];
        }
        else if (p.children()[1].pid() == sign * 20433 && p.children()[0].pid() == iD) {
          Ds1 = p.children()[1];
        }
        else
          continue;
        // find children of the Ds1 meson
        Particle Ds;
        if (Ds1.children().size() != 2) continue;
        if (Ds1.children()[0].abspid() == 431 && Ds1.children()[1].abspid() == 22)
          Ds = Ds1.children()[0];
        else if (Ds1.children()[1].abspid() == 431 && Ds1.children()[0].abspid() == 22)
          Ds = Ds1.children()[1];
        else
          continue;
        // boost to rest frame
        LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
        FourMomentum pDs1 = boostB.transform(Ds1.momentum());
        FourMomentum pDs = boostB.transform(Ds.momentum());
        LorentzTransform boostDs1 = LorentzTransform::mkFrameTransformFromBeta(pDs1.betaVec());
        pDs = boostDs1.transform(pDs);
        Vector3 axis = pDs1.p3().unit();
        double cTheta = axis.dot(pDs.p3().unit());
        _h->fill(cTheta);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2004_I656424);

}