Rivet analyses

title: BABAR_2007_I747154

Dalitz plot analysis of $D^0\to \pi^+\pi^-\pi^0$

Experiment: BABAR (PEP-II)

Inspire ID: 747154

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 99 (2007) 251801

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0 -> pi+pi-pi0, original e+e->Upsilon(4S)

Measurement of the mass distributions in the decay $D^0\to \pi^+\pi^-\pi^0$. 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:BABAR_2007_I747154.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D0 -> pi+pi-pi0 class BABAR_2007_I747154 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I747154);


/// @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(_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 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);
    _dalitz->fill(mminus, mplus);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_pi[0]);
  normalize(_h_pi[1]);
  normalize(_dalitz);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pi[2];
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2007_I747154);

} ```