Rivet analyses

Dalitz plot analysis of D0 → π+π−π0

Experiment: BABAR (PEP-II)

Inspire ID: 1441203

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 93 (2016) 11, 112014

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of the mass distributions in the decay D0 → π+π−π0. The data were read from the plots in the paper and the background subtracted. Resolution/acceptance effects have been unfolded and given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:BABAR_2016_I1441203.cc

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

namespace Rivet {


  /// @brief D0 -> pi+pi-pi0
  class BABAR_2016_I1441203 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2016_I1441203);


    /// @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_pi[0], 1, 1, 1);
      book(_h_pi[1], 1, 1, 2);
      book(_h_pi[2], 1, 1, 3);
      book(_dalitz, "dalitz", 50, 0., 3.2, 50, 0.0, 3.2);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{211, 1}, {-211, 1}, {111, 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& pi0 = D0.decayProducts()[ix].at(111);
        const Particles& pip = D0.decayProducts()[ix].at(sign * 211);
        const Particles& pim = D0.decayProducts()[ix].at(-sign * 211);
        double mneut = (pim[0].momentum() + pip[0].momentum()).mass2();
        // if(mneut>475*MeV && mneut<505*MeV) continue;
        double mplus = (pip[0].momentum() + pi0[0].momentum()).mass2();
        double mminus = (pim[0].momentum() + pi0[0].momentum()).mass2();
        _h_pi[0]->fill(mplus);
        _h_pi[1]->fill(mminus);
        _h_pi[2]->fill(mneut);
        _dalitz->fill(mplus, mminus);
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_pi[3];
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2016_I1441203);

}