Rivet analyses

title: BABAR_2014_I1287632

Dalitz plot analysis of $\eta_c\to K^+K^-\eta$ and $\eta_c\to K^+K^-\pi^0$

Experiment: BABAR (PEP-II)

Inspire ID: 1287632

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 89 (2014) 11, 112004

Beams: * *

Beam energies: ANY

Run details: - Any process producing eta_c (originally gamma gamma -> eta_c)

Measurement of the mass distributions in the decays $\eta_c\to K^+K^-\eta$ and $\eta_c\to K^+K^-\pi^0$ by BaBar. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. Also the sideband background from the plots has been subtracted. It is also not clear that any resolution effects have been unfolded.

Source code:BABAR_2014_I1287632.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief eta_c -> K+K- eta or pi0 class BABAR_2014_I1287632 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2014_I1287632);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 441);
  declare(ufs, "UFS");
  DecayedParticles ETAC(ufs);
  ETAC.addStable(PID::PI0);
  ETAC.addStable(PID::ETA);
  declare(ETAC, "ETAC");
  // histos
  book(_h_KK[0], 1, 1, 1);
  book(_h_KK[1], 2, 1, 1);
  book(_h_Kpeta, 1, 1, 2);
  book(_h_Kmeta, 1, 1, 3);
  book(_h_Kppi, 2, 1, 2);
  book(_h_Kmpi, 2, 1, 3);
  book(_dalitz[0], "dalitz_1", 50, 0.5, 7.0, 50, 0.5, 7.0);
  book(_dalitz[1], "dalitz_2", 50, 0.2, 6.5, 50, 0.2, 6.5);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{321, 1}, {-321, 1}, {111, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{321, 1}, {-321, 1}, {221, 1}};
  DecayedParticles ETAC = apply<DecayedParticles>(event, "ETAC");
  // loop over particles
  for (unsigned int ix = 0; ix < ETAC.decaying().size(); ++ix) {
    int imode = 0;
    if (ETAC.modeMatches(ix, 3, mode1))
      imode = 0;
    else if (ETAC.modeMatches(ix, 3, mode2))
      imode = 1;
    else
      continue;
    const Particle& Kp = ETAC.decayProducts()[ix].at(321)[0];
    const Particle& Km = ETAC.decayProducts()[ix].at(-321)[0];
    if (imode == 0 && ETAC.decaying()[ix].mass() > 2.922 && ETAC.decaying()[ix].mass() < 3.036) {
      const Particle& pi0 = ETAC.decayProducts()[ix].at(111)[0];
      double mplus = (Kp.momentum() + pi0.momentum()).mass2();
      double mminus = (Km.momentum() + pi0.momentum()).mass2();
      double mKK = (Kp.momentum() + Km.momentum()).mass2();
      _h_KK[1]->fill(mKK);
      _h_Kppi->fill(mplus);
      _h_Kmpi->fill(mminus);
      _dalitz[1]->fill(mplus, mminus);
    }
    else if (imode == 1 && ETAC.decaying()[ix].mass() > 2.910 && ETAC.decaying()[ix].mass() < 3.03) {
      const Particle& eta = ETAC.decayProducts()[ix].at(221)[0];
      double mplus = (Kp.momentum() + eta.momentum()).mass2();
      double mminus = (Km.momentum() + eta.momentum()).mass2();
      double mKK = (Kp.momentum() + Km.momentum()).mass2();
      _h_KK[0]->fill(mKK);
      _h_Kpeta->fill(mplus);
      _h_Kmeta->fill(mminus);
      _dalitz[0]->fill(mplus, mminus);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_KK[0]);
  normalize(_h_KK[1]);
  normalize(_h_Kmpi);
  normalize(_h_Kppi);
  normalize(_h_Kmeta);
  normalize(_h_Kpeta);
  normalize(_dalitz[0]);
  normalize(_dalitz[1]);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_KK[2], _h_Kmeta, _h_Kpeta, _h_Kmpi, _h_Kppi;
Histo2DPtr _dalitz[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2014_I1287632);

} ```