Rivet analyses

title: BESIII_2022_I2030993

Dalitz decay of $D_s^+\to\pi^+\pi^0\eta^\prime$

Experiment: BESIII (BEPC)

Inspire ID: 2030993

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2202.04232

Beams: * *

Beam energies: ANY

Run details: - Any process producing D_s+ mesons

Measurement of the mass distributions in the decay $D^+_s\to \pi^+\pi^0\eta^\prime$ by BES. The data were read from the plots in the paper. It is also not clear that any resolution effects have been unfolded.

Source code:BESIII_2022_I2030993.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D_s+ -> pi+ pi0 eta' class BESIII_2022_I2030993 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2030993);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 431);
  declare(ufs, "UFS");
  DecayedParticles DS(ufs);
  DS.addStable(PID::PI0);
  DS.addStable(PID::K0S);
  DS.addStable(PID::ETAPRIME);
  declare(DS, "DS");
  // histograms
  book(_h_etapip, 1, 1, 1);
  book(_h_etapi0, 1, 1, 2);
  book(_h_pipi, 1, 1, 3);
  book(_dalitz, "dalitz", 50, 0., 1.1, 50, 1, 3.5);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{211, 1}, {111, 1}, {331, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-211, 1}, {111, 1}, {331, 1}};
  DecayedParticles DS = apply<DecayedParticles>(event, "DS");
  // loop over particles
  for (unsigned int ix = 0; ix < DS.decaying().size(); ++ix) {
    int sign = 1;
    if (DS.decaying()[ix].pid() > 0 && DS.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (DS.decaying()[ix].pid() < 0 && DS.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particle& pip = DS.decayProducts()[ix].at(sign * 211)[0];
    const Particle& pi0 = DS.decayProducts()[ix].at(111)[0];
    const Particle& eta = DS.decayProducts()[ix].at(331)[0];
    double mplus = (eta.momentum() + pip.momentum()).mass2();
    double mzero = (eta.momentum() + pi0.momentum()).mass2();
    double mpipi = (pip.momentum() + pi0.momentum()).mass2();
    _dalitz->fill(mpipi, mplus);
    _h_pipi->fill(sqrt(mpipi));
    _h_etapip->fill(sqrt(mplus));
    _h_etapi0->fill(sqrt(mzero));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_pipi, 1., false);
  normalize(_h_etapip, 1., false);
  normalize(_h_etapi0, 1., false);
  normalize(_dalitz, 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pipi, _h_etapip, _h_etapi0;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2022_I2030993);

} ```