Rivet analyses

title: CLEOC_2008_I779705

Mass distributions in $D^0\to\eta\pi^+\pi^-$ decays

Experiment: CLEOC (CESR)

Inspire ID: 779705

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D77 (2008) 092003

Beams: * *

Beam energies: ANY

Run details: - Any process producing $d^0$ mesons, originally e+e-

Measurement of mass distributions in $D^0\to\eta\pi^+\pi^-$ decays by the CLEO experiment.

Source code:CLEOC_2008_I779705.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D0 -> eta pi+pi- decays class CLEOC_2008_I779705 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2008_I779705);


/// @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_eta_pi, 1, 1, 1);
  book(_h_pi_pi, 1, 1, 2);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{211, 1}, {-211, 1}, {221, 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& eta = D0.decayProducts()[ix].at(221);
    const Particles& pip = D0.decayProducts()[ix].at(sign * 211);
    const Particles& pim = D0.decayProducts()[ix].at(-sign * 211);
    _h_eta_pi->fill((pip[0].momentum() + eta[0].momentum()).mass());
    _h_pi_pi->fill((pip[0].momentum() + pim[0].momentum()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_eta_pi);
  normalize(_h_pi_pi);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_eta_pi, _h_pi_pi;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOC_2008_I779705);

} ```