Rivet analyses

title: BABAR_2006_I719581

Decay asymmetries in the decay of $\Omega^-$ baryons produced in $\Xi^0_c$ and $\Omega_c^0$ 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 $\Xi^0_c\to\Omega^-K^+$ and $\Omega^-_c\to\Omega^-\pi^+$ by the BaBar experiment. In both cases the decay mode $\Omega^-\to\Lambda^0K^-$ was used. This analysis is useful for testing spin correlations in hadron decays.

Source code:BABAR_2006_I719581.cc

```c++ // -- 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);

} ```