Rivet analyses

title: BABAR_2010_I853279

Dalitz plot analysis of $D^0\to K^0_S\pi^+\pi^-$ and $D^0\to K^0_SK^+K^-$

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 $D^0\to K^0_S\pi^+\pi^-$ and $D^0\to K^0_SK^+K^-$ 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++ // -- 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);

} ```