Rivet analyses

Helicity and decay angles for the decay Ξc(2790)+ → Ξc*0( → Ξc+π−)π+’

Experiment: BELLE (KEKB)

Inspire ID: 1809180

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 103 (2021) 11, L111101

Beams: e+ e-

Beam energies: (5.3, 5.3)GeV

Run details: - e+e- to hadrons

Measurement of the helicity and decay angles for the decay Ξc(2790)+ → Ξc*0( → Ξc+π−)π+. The PDG code for this particle is not specified and which multiplet it belongs to is unclear. The default is to use 204232, i.e. it is in the same multiplet as the Roper resonance, but this can be changed using the PID option.

Source code:BELLE_2021_I1809180.cc

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

namespace Rivet {


  /// @brief Xi_c(2970) decays
  class BELLE_2021_I1809180 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2021_I1809180);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // set the PDG code
      _pid = getOption<double>("PID", 103242);
      // projections
      declare(UnstableParticles(Cuts::abspid==_pid), "UFS");
      for(unsigned int ix=0;ix<2;++ix)
    book(_h[ix],1+ix,1,1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Get beams and average beam momentum
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
    // xp cut
    double xp = p.momentum().p3().mod()/sqrt(0.25*sqrtS()-p.mass2());
    if (xp<.7) continue;
    // find the decay products
    // first decay
    if(p.children().size()!=2) continue;
    Particle XiStar,pi1;
    if(p.children()[0].abspid()==4314 &&
       p.children()[1].abspid()== 211) {
      XiStar = p.children()[0];
      pi1    = p.children()[1];
    }
    else if(p.children()[1].abspid()==4314 &&
        p.children()[0].abspid()== 211) {
      XiStar = p.children()[1];
      pi1    = p.children()[0];
    }
    else
      continue;
    Vector3 axis1 = p.momentum().p3().unit();
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    FourMomentum ppi1 = boost.transform(pi1.momentum());
    _h[0]->fill(axis1.dot(ppi1.p3().unit()));
    Particle pi2;
    // second decay
    if(XiStar.children()[0].abspid()==4232 &&
       XiStar.children()[1].abspid()== 211) {
      pi2    = XiStar.children()[1];
    }
    else if(XiStar.children()[1].abspid()== 4232 &&
        XiStar.children()[0].abspid()== 211) {
      pi2    = XiStar.children()[0];
    }
    else
      continue;
    FourMomentum pXiStar = boost.transform(XiStar.momentum());
    FourMomentum ppi2    = boost.transform(pi2.momentum());
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pXiStar.betaVec());
    ThreeVector axis2 = pXiStar.p3().unit();
    ppi2 =  boost2.transform(ppi2);
    _h[1]->fill(axis2.dot(ppi2.p3().unit()));
      }
    }


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

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(BELLE_2021_I1809180);

}