Rivet analyses

title: BESIII_2022_I2084294

Dalitz decay of $D^+_s\to K^+\pi^+\pi^-$

Experiment: BESIII (BEPC)

Inspire ID: 2084294

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2205.08844

Beams: * *

Beam energies: ANY

Run details: - Any process producing D_s+ mesons

Measurement of the mass distributions in the decay $D^+_s\to K^+\pi^+\pi^-$ by BES. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. It is also not clear that any resolution effects have been unfolded.

Source code:BESIII_2022_I2084294.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Ds+ -> K+ pi+ pi- class BESIII_2022_I2084294 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2084294);


/// @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::ETA);
  DS.addStable(PID::ETAPRIME);
  declare(DS, "DS");
  // histograms
  book(_h_Kpip, 1, 1, 1);
  book(_h_Kpim, 1, 1, 2);
  book(_h_pipi, 1, 1, 3);
  book(_dalitz, "dalitz", 50, 0., 2.3, 50, 0.3, 3.5);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{321, 1}, {211, 1}, {-211, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {-211, 1}, {211, 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& Kp = DS.decayProducts()[ix].at(sign * 321)[0];
    const Particle& pip = DS.decayProducts()[ix].at(sign * 211)[0];
    const Particle& pim = DS.decayProducts()[ix].at(-sign * 211)[0];
    double mp = (Kp.momentum() + pip.momentum()).mass2();
    double mm = (Kp.momentum() + pim.momentum()).mass2();
    double mpipi = (pip.momentum() + pim.momentum()).mass2();
    _dalitz->fill(mpipi, mm);
    if (mpipi < sqr(.4676) || mpipi > sqr(0.5276)) {
      _h_pipi->fill(sqrt(mpipi));
      _h_Kpip->fill(sqrt(mp));
      _h_Kpim->fill(sqrt(mm));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_Kpip);
  normalize(_h_Kpim);
  normalize(_h_pipi);
  normalize(_dalitz);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_Kpip, _h_Kpim, _h_pipi;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2022_I2084294);

} ```