Rivet analyses

Dalitz plot analysis of D+ → K+K+K−

Experiment: LHCB (LHC)

Inspire ID: 1720423

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - JHEP 04 (2019) 063

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+ -> K+ K+ K-

Measurement of the mass distributions in the decay D+ → K+K+K−. The data were read extracted from the plots in the paper and the backgrounds subtracted. Resolution/acceptance effects have been not unfolded and given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:LHCB_2019_I1720423.cc

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

namespace Rivet {


  /// @brief D+ -> K+K+K-
  class LHCB_2019_I1720423 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2019_I1720423);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(UnstableParticles(), "UFS");
      book(_h_KpKm[0],1,1,1);
      book(_h_KpKp   ,1,1,2);
      book(_h_KpKm[1],1,1,3);
      book(_h_KpKm[2],1,1,4);
      book(_dalitz, "dalitz",50,0.9,1.8,50,1.1,1.9);
    }

    void findDecayProducts(const Particle & mother, unsigned int & nstable,
               Particles & Kp , Particles & Km) {
      for(const Particle & p : mother.children()) {
        int id = p.pid();
        if ( id == PID::PIPLUS || id == PID::PIMINUS ||
         id == PID::K0S   || id == PID::K0L ||
         id == PID::PI0 ) {
      ++nstable;
    }
    else if (id == PID::KPLUS) {
      Kp.push_back(p);
      ++nstable;
    }
    else if (id == PID::KMINUS) {
      Km.push_back(p);
      ++nstable;
    }
    else if ( !p.children().empty() ) {
      findDecayProducts(p, nstable, Kp, Km);
    }
    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 Kp, Km;
    findDecayProducts(meson, nstable, Kp, Km);
    if(nstable !=3) continue;
    if(meson.pid()<0) {
      swap(Km,Kp);
    }
    if (Km.size()==1&&Kp.size()==2) {
      double m1 = (Km[0].momentum()+Kp[0].momentum()).mass2();
      double m2 = (Km[0].momentum()+Kp[1].momentum()).mass2();
      double m3 = (Kp[0].momentum()+Kp[1].momentum()).mass2();
      if(m1>m2) swap(m1,m2);
      _dalitz->fill(m1,m2);
      _h_KpKm[0]->fill(m1);
      _h_KpKm[0]->fill(m2);
      _h_KpKm[2]->fill(m1);
      _h_KpKm[1]->fill(m2);
      _h_KpKp->fill(m3);
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<3;++ix)
    normalize(_h_KpKm[ix]);
      normalize(_h_KpKp);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_KpKm[3],_h_KpKp;
    Histo2DPtr _dalitz;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(LHCB_2019_I1720423);

}