Rivet analyses

Decay asymmetries in the decay of Ω− baryons produced in Ξc0 and Ωc0 decays

Experiment: BABAR (PEP-II)

Inspire ID: 719581

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 112001

Beams: * *

Beam energies: ANY

Run details: - Any process producing Xi_c0 and Omega_c0 baryons

Measurement of the decay asymmetries in Ξc0 → Ω−K+ and Ωc− → Ω−π+ by the BaBar experiment. In both cases the decay mode Ω− → Λ0K− was used. This analysis is useful for testing spin correlations in hadron decays.

Source code:BABAR_2006_I719581.cc

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

namespace Rivet {


  /// @brief Omega decay asymmetries
  class BABAR_2006_I719581 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I719581);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableParticles(), "UFS");
      // Book histograms
      book(_h_ctheta_xic, 1, 1, 1);
      book(_h_ctheta_omegac, 2, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // loop over Xi_c0 baryons and Omega_c0 baryons
      for (const Particle& baryon :
           apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid == 4132 || Cuts::abspid == 4332)) {
        int sign = baryon.pid() / baryon.abspid();
        if (baryon.children().size() != 2) continue;
        Particle baryon1, meson1;
        if (baryon.abspid() == 4132) {
          if (baryon.children()[0].pid() == sign * 3334 && baryon.children()[1].pid() == sign * 321) {
            baryon1 = baryon.children()[0];
            meson1 = baryon.children()[1];
          }
          else if (baryon.children()[1].pid() == sign * 3332 && baryon.children()[0].pid() == sign * 321) {
            baryon1 = baryon.children()[1];
            meson1 = baryon.children()[0];
          }
          else
            continue;
        }
        else {
          if (baryon.children()[0].pid() == sign * 3334 && baryon.children()[1].pid() == sign * 211) {
            baryon1 = baryon.children()[0];
            meson1 = baryon.children()[1];
          }
          else if (baryon.children()[1].pid() == sign * 3334 && baryon.children()[0].pid() == sign * 211) {
            baryon1 = baryon.children()[1];
            meson1 = baryon.children()[0];
          }
          else
            continue;
        }
        Particle baryon2, meson2;
        if (baryon1.children()[0].pid() == sign * 3122 && baryon1.children()[1].pid() == -sign * 321) {
          baryon2 = baryon1.children()[0];
          meson2 = baryon1.children()[1];
        }
        else if (baryon1.children()[1].pid() == sign * 3122 && baryon1.children()[0].pid() == -sign * 321) {
          baryon2 = baryon1.children()[1];
          meson2 = baryon1.children()[0];
        }
        else
          continue;
        // first boost to the Xic/Omegac rest frame
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(baryon.momentum().betaVec());
        FourMomentum pbaryon1 = boost1.transform(baryon1.momentum());
        FourMomentum pbaryon2 = boost1.transform(baryon2.momentum());
        // to omega rest frame
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pbaryon1.betaVec());
        Vector3 axis = pbaryon1.p3().unit();
        FourMomentum pp = boost2.transform(pbaryon2);
        // calculate angle
        double cTheta = pp.p3().unit().dot(axis);
        if (baryon.abspid() == 4132)
          _h_ctheta_xic->fill(cTheta, 1.);
        else
          _h_ctheta_omegac->fill(cTheta, 1.);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      normalize(_h_ctheta_xic);
      normalize(_h_ctheta_omegac);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_ctheta_xic, _h_ctheta_omegac;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2006_I719581);


}