Rivet analyses

Dalitz plot analysis of D0 → KS0π+π− and D0 → KS0K+K−

Experiment: BABAR (PEP-II)

Inspire ID: 853279

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 105 (2010) 081803

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0

Measurement of Kinematic distributions in the decays D0 → KS0π+π− and D0 → KS0K+K− by BaBar. The data were read from the plots in the paper. Resolution/acceptance effects have been not unfolded. Given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:BABAR_2010_I853279.cc

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

namespace Rivet {


  /// @brief D0 -> KS0 pi+pi- and K+K-
  class BABAR_2010_I853279 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2010_I853279);


    /// @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_Kpim, 1, 1, 1);
      book(_h_Kpip, 1, 1, 2);
      book(_h_pipi, 1, 1, 3);
      book(_dalitz[0], "dalitz1", 50, 0.3, 3.2, 50, 0.3, 3.2);
      book(_h_K0Km, 1, 1, 4);
      book(_h_K0Kp, 1, 1, 5);
      book(_h_KpKm, 1, 1, 6);
      book(_dalitz[1], "dalitz2", 50, 0.9, 1.9, 50, 0.9, 1.9);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      static const map<PdgId, unsigned int>& modePi = {{310, 1}, {211, 1}, {-211, 1}};
      static const map<PdgId, unsigned int>& modeK = {{310, 1}, {321, 1}, {-321, 1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for (unsigned int ix = 0; ix < D0.decaying().size(); ++ix) {
        int sign = D0.decaying()[ix].pid() / 421;
        // KS0 pi+pi-
        if (D0.modeMatches(ix, 3, modePi)) {
          const Particles& pip = D0.decayProducts()[ix].at(sign * 211);
          const Particles& pim = D0.decayProducts()[ix].at(-sign * 211);
          const Particles& K0 = D0.decayProducts()[ix].at(310);
          double mminus = (pim[0].momentum() + K0[0].momentum()).mass2();
          double mplus = (pip[0].momentum() + K0[0].momentum()).mass2();
          double mpipi = (pip[0].momentum() + pim[0].momentum()).mass2();
          _h_Kpip->fill(mplus);
          _h_Kpim->fill(mminus);
          _h_pipi->fill(mpipi);
          _dalitz[0]->fill(mminus, mplus);
        }
        else if (D0.modeMatches(ix, 3, modeK)) {
          const Particles& Kp = D0.decayProducts()[ix].at(sign * 321);
          const Particles& Km = D0.decayProducts()[ix].at(-sign * 321);
          const Particles& K0 = D0.decayProducts()[ix].at(310);
          double mminus = (Km[0].momentum() + K0[0].momentum()).mass2();
          double mplus = (Kp[0].momentum() + K0[0].momentum()).mass2();
          double mKK = (Kp[0].momentum() + Km[0].momentum()).mass2();
          _h_K0Kp->fill(mplus);
          _h_K0Km->fill(mminus);
          _h_KpKm->fill(mKK);
          _dalitz[1]->fill(mplus, mKK);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_Kpim);
      normalize(_h_Kpip);
      normalize(_h_pipi);
      normalize(_dalitz[0]);
      normalize(_h_K0Km);
      normalize(_h_K0Kp);
      normalize(_h_KpKm);
      normalize(_dalitz[1]);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kpim, _h_pipi, _h_Kpip;
    Histo1DPtr _h_K0Km, _h_KpKm, _h_K0Kp;
    Histo2DPtr _dalitz[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2010_I853279);

}