Rivet analyses

title: BESIII_2021_I1921801

Mass distributions in $\psi(2S)\to\omega K^0_SK^0_S$

Experiment: BESIII (BEPC)

Inspire ID: 1921801

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 104 (2021) 9, 092003

Beams: * *

Beam energies: ANY

Run details: - Any process producing psi(2S), originally e+e-

Measurement of mass distributions in $\psi(2S)\to\omega K^0_SK^0_S$ by BES. N.B. data read from plots and may not be corrected, no difference between $K_{S1}^0$ and $K^0_{S2}$ so these are symeterised.

Source code:BESIII_2021_I1921801.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief psi(2S) -> omega KS0 KS0 class BESIII_2021_I1921801 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1921801);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 100443);
  declare(ufs, "UFS");
  DecayedParticles psi2S(ufs);
  psi2S.addStable(PID::PI0);
  psi2S.addStable(PID::K0S);
  psi2S.addStable(PID::ETA);
  psi2S.addStable(PID::ETAPRIME);
  psi2S.addStable(PID::OMEGA);
  declare(psi2S, "psi2S");
  // histograms
  for (unsigned int ix = 0; ix < 3; ++ix) book(_h[ix], 1, 1, 1 + ix);
  book(_dalitz, "dalitz", 50, 1., 11., 50, 1., 11.);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // define the decay mode
  static const map<PdgId, unsigned int>& mode = {{310, 2}, {223, 1}};
  DecayedParticles psi2S = apply<DecayedParticles>(event, "psi2S");
  // loop over particles
  for (unsigned int ix = 0; ix < psi2S.decaying().size(); ++ix) {
    if (!psi2S.modeMatches(ix, 3, mode)) continue;
    const Particles& K0 = psi2S.decayProducts()[ix].at(310);
    const Particles& omega = psi2S.decayProducts()[ix].at(223);
    double m2Komega[2] = {(K0[0].momentum() + omega[0].momentum()).mass2(),
                          (K0[1].momentum() + omega[0].momentum()).mass2()};
    for (unsigned int ix = 0; ix < 2; ++ix) {
      double mKo = sqrt(m2Komega[ix]);
      _h[0]->fill(mKo);
      _h[1]->fill(mKo);
    }
    _h[2]->fill((K0[0].momentum() + K0[1].momentum()).mass());
    _dalitz->fill(m2Komega[0], m2Komega[1]);
    _dalitz->fill(m2Komega[1], m2Komega[0]);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h[ix], 1., false);
  normalize(_dalitz);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[3];
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2021_I1921801);

} ```