Rivet analyses

Mass distributions in D0 → ηπ+π− decays

Experiment: CLEOC (CESR)

Inspire ID: 779705

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D77 (2008) 092003

Beams: * *

Beam energies: ANY

Run details: - Any process producing d0 mesons, originally e+e-

Measurement of mass distributions in D0 → ηπ+π− decays by the CLEO experiment.

Source code:CLEOC_2008_I779705.cc

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

namespace Rivet {


  /// @brief D0 -> eta pi+pi- decays
  class CLEOC_2008_I779705 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2008_I779705);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==421);
      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");
      // histograms
      book(_h_eta_pi,1,1,1);
      book(_h_pi_pi ,1,1,2);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 211,1},{-211,1}, {221,1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
        if( !D0.modeMatches(ix,3,mode)  ) continue;
        int sign = D0.decaying()[ix].pid()/421;
        const Particles & eta = D0.decayProducts()[ix].at(221);
        const Particles & pip = D0.decayProducts()[ix].at( sign*211);
        const Particles & pim = D0.decayProducts()[ix].at(-sign*211);
        _h_eta_pi->fill((pip[0].momentum()+eta[0].momentum()).mass());
        _h_pi_pi ->fill((pip[0].momentum()+pim[0].momentum()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_eta_pi);
      normalize(_h_pi_pi );
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_eta_pi,_h_pi_pi;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(CLEOC_2008_I779705);

}