Rivet analyses

Dalitz plot analysis of D+ → K−π+π+

Experiment: FOCUS (Fermilab)

Inspire ID: 750701

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 653 (2007) 1-11

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decay D+ → K−π+π+. The data were read from the plots in the paper. 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:FOCUS_2007_I750701.cc

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

namespace Rivet {


  /// @brief D+ -> K-pi+pi+
  class FOCUS_2007_I750701 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(FOCUS_2007_I750701);


    /// @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 DP(ufs);
      DP.addStable(PID::PI0);
      declare(DP, "DP");
      // histos
      book(_h_low, 1, 1, 1);
      book(_h_high, 1, 1, 2);
      book(_dalitz, "dalitz", 50, 0., 3.1, 50, 0.3, 3.1);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{211, 2}, {-321, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-211, 2}, {321, 1}};
      // Loop over D+ mesons
      DecayedParticles DP = apply<DecayedParticles>(event, "DP");
      for (unsigned int ix = 0; ix < DP.decaying().size(); ++ix) {
        int sign = 1;
        if (DP.modeMatches(ix, 3, mode))
          sign = 1;
        else if (DP.modeMatches(ix, 3, modeCC))
          sign = -1;
        else
          continue;
        const Particles& pip = DP.decayProducts()[ix].at(sign * 211);
        const Particle& Km = DP.decayProducts()[ix].at(-sign * 321)[0];
        double mplus = (Km.momentum() + pip[0].momentum()).mass2();
        double mminus = (Km.momentum() + pip[1].momentum()).mass2();
        if (mplus < mminus) swap(mplus, mminus);
        _h_low->fill(mminus);
        _h_high->fill(mplus);
        _dalitz->fill(mminus, mplus);
        _dalitz->fill(mplus, mminus);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_low);
      normalize(_h_high);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_high, _h_low;
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(FOCUS_2007_I750701);

}