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FOCUS_2004_I654030

Dalitz decay of $D^+$ and $D^+_s\to K^+\pi^+\pi^-$
Experiment: FOCUS (Fermilab)
Inspire ID: 654030
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Lett.B 601 (2004) 10-19
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing D+ or D_s+ mesons

Measurement of the mass distributions in the decays $D^+$ and $D^+_s\to K^+\pi^+\pi^-$ by FOCUS. 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: FOCUS_2004_I654030.cc 
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief D+/Ds+ -> K+ pi+ pi-
  class FOCUS_2004_I654030 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(FOCUS_2004_I654030);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==411 or
						Cuts::abspid==431);
      declare(ufs, "UFS");
      DecayedParticles DD(ufs);
      DD.addStable(PID::PI0);
      DD.addStable(PID::K0S);
      declare(DD, "DD");
      // histograms
      for(unsigned int ix=0;ix<2;++ix) {
	book(_h_Kpim[ix],1+ix,1,1);
	book(_h_pipi[ix],1+ix,1,2);
	book(_dalitz[ix],"dalitz_"+to_str(ix+1),50,0.3,3.5,50,0.,2.3);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 211,1}, { 321,1}, {-211,1}};
      static const map<PdgId,unsigned int> & modeCC = { {-211,1}, {-321,1}, { 211,1}};
      DecayedParticles DD = apply<DecayedParticles>(event, "DD");
      // loop over particles
      for(unsigned int ix=0;ix<DD.decaying().size();++ix) {
	int sign = 1;
	if (DD.decaying()[ix].pid()>0 && DD.modeMatches(ix,3,mode)) {
	  sign=1;
	}
	else if  (DD.decaying()[ix].pid()<0 && DD.modeMatches(ix,3,modeCC)) {
	  sign=-1;
	}
	else
	  continue;
	const Particle & Kp  = DD.decayProducts()[ix].at( sign*321)[0];
	const Particle & pip = DD.decayProducts()[ix].at( sign*211)[0];
	const Particle & pim = DD.decayProducts()[ix].at(-sign*211)[0];
	double mm    = (Kp .momentum()+pim.momentum()).mass2();
	double mpipi = (pip.momentum()+pim.momentum()).mass2();
	unsigned int iloc = DD.decaying()[ix].abspid()==411 ? 0 : 1;
	_dalitz[iloc]->fill(mm,mpipi);
	_h_pipi[iloc]->fill(mpipi);
	_h_Kpim[iloc]->fill(mm);
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kpim[2],_h_pipi[2];
    Histo2DPtr _dalitz[2];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(FOCUS_2004_I654030);

}