Rivet analyses

Mass distributions in the decay D⁺ → K_S⁰π⁺π⁺π⁻

Experiment: BESIII (BEPC)

Inspire ID: 1714778

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 100 (2019) 7, 072008

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of the mass distributions in the decay D⁺ → K_S⁰π⁺π⁺π⁻ by BES. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. It is also not clear that any resolution effects have been unfolded.

Source code:`BESIII_2019_I1714778.cc`

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

namespace Rivet {


  /// @brief D+ -> KS0 pi+pi+pi-
  class BESIII_2019_I1714778 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1714778);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==411);
      declare(ufs, "UFS");
      DecayedParticles D0(ufs);
      D0.addStable(PID::PI0);
      D0.addStable(PID::K0S);
      D0.addStable(PID::ETA);
      D0.addStable(PID::ETAPRIME);
      declare(D0, "D0");
      // histos
      for(unsigned int ix=0;ix<9;++ix)
    book(_h[ix],1,1,1+ix);
    }

    void findDecayProducts(const Particle & mother, unsigned int & nstable,
               Particles & pip , Particles & pim , Particles & K0) {
      for(const Particle & p : mother.children()) {
        int id = p.pid();
        if (id == PID::PIPLUS) {
      pip.push_back(p);
      ++nstable;
    }
    else if (id == PID::PIMINUS) {
      pim.push_back(p);
      ++nstable;
    }
    else if (id == PID::K0S) {
      K0.push_back(p);
      ++nstable;
    }
    else if (id == PID::KPLUS ||id == PID::KMINUS  ||
         id == PID::PI0||id == PID::K0L) {
          ++nstable;
        }
    else if ( !p.children().empty() ) {
      findDecayProducts(p, nstable, pip, pim, K0);
    }
    else
      ++nstable;
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      for(const Particle& meson : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid== 411)) {
    unsigned int nstable(0);
    Particles pip, pim, K0;
    findDecayProducts(meson, nstable, pip, pim, K0);
    if (nstable!=4) continue;
    if(meson.pid()<0) {
      swap(pim,pip);
    }
    if(pip.size()==2&&pim.size()==1&&K0.size()==1) {
      double mpippim[2] = {(pim[0].momentum()+pip[0].momentum()).mass(), 
                   (pim[0].momentum()+pip[1].momentum()).mass()};
      if(mpippim[0]>mpippim[1]) {
        swap(  pip[0],  pip[1]);
        swap(mpippim[0],mpippim[1]);
      }
      _h[0]->fill((K0 [0].momentum()+pim[0].momentum()).mass());
      _h[1]->fill((K0 [0].momentum()+pip[0].momentum()).mass());
      _h[2]->fill((K0 [0].momentum()+pip[1].momentum()).mass());
      _h[3]->fill(mpippim[0]);
      _h[4]->fill(mpippim[1]);
      _h[5]->fill((K0 [0].momentum()+pim[0].momentum()+pip[0].momentum()).mass());
      _h[6]->fill((K0 [0].momentum()+pim[0].momentum()+pip[1].momentum()).mass());
      _h[7]->fill((pim[0].momentum()+pip[0].momentum()+pip[1].momentum()).mass());
      _h[8]->fill((pip[0].momentum()+pip[1].momentum()).mass());
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<9;++ix)
    normalize(_h[ix],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[9];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2019_I1714778);

}

Rivet analyses

Mass distributions in the decay D+ → KS0π+π+π−

Source code:BESIII_2019_I1714778.cc

Mass distributions in the decay D⁺ → K_S⁰π⁺π⁺π⁻

Source code:`BESIII_2019_I1714778.cc`