Rivet analyses

title: BELLE_2022_I2160445

Mass distributions in $\Lambda_c^+\to p K^0_S K^0_S$ and $\Lambda_c^+\to p K^0_S \eta$

Experiment: BELLE (KEKB)

Inspire ID: 2160445

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2210.01995

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of the mass distributions in the decays $\Lambda_c^+\to p K^0_S K^0_S$ and $\Lambda_c^+\to p K^0_S \eta$ by BELLE. The data were read from the plots in the paper but have been corrected for efficiency/acceptance.

Source code:BELLE_2022_I2160445.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda_c+ -> p 2K0S and p K0S eta class BELLE_2022_I2160445 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2022_I2160445);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 4122);
  declare(ufs, "UFS");
  DecayedParticles LAMBDAC(ufs);
  LAMBDAC.addStable(PID::PI0);
  LAMBDAC.addStable(PID::K0S);
  LAMBDAC.addStable(PID::ETA);
  declare(LAMBDAC, "LAMBDAC");
  // histograms
  for (unsigned int ix = 0; ix < 2; ++ix)
    for (unsigned int iy = 0; iy < 2 + ix; ++iy) book(_h[ix][iy], 1 + ix, 1, 1 + iy);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{PID::PROTON, 1}, {310, 2}};
  static const map<PdgId, unsigned int>& mode1CC = {{-PID::PROTON, 1}, {310, 2}};
  static const map<PdgId, unsigned int>& mode2 = {{PID::PROTON, 1}, {310, 1}, {221, 1}};
  static const map<PdgId, unsigned int>& mode2CC = {{-PID::PROTON, 1}, {310, 1}, {221, 1}};
  DecayedParticles LAMBDAC = apply<DecayedParticles>(event, "LAMBDAC");
  // loop over particles
  for (unsigned int ix = 0; ix < LAMBDAC.decaying().size(); ++ix) {
    int sign = 1, mode = -1;
    if (LAMBDAC.decaying()[ix].pid() > 0 && LAMBDAC.modeMatches(ix, 3, mode1)) {
      sign = 1;
      mode = 0;
    }
    else if (LAMBDAC.decaying()[ix].pid() < 0 && LAMBDAC.modeMatches(ix, 3, mode1CC)) {
      sign = -1;
      mode = 0;
    }
    else if (LAMBDAC.decaying()[ix].pid() > 0 && LAMBDAC.modeMatches(ix, 3, mode2)) {
      sign = 1;
      mode = 1;
    }
    else if (LAMBDAC.decaying()[ix].pid() < 0 && LAMBDAC.modeMatches(ix, 3, mode2CC)) {
      sign = -1;
      mode = 1;
    }
    else
      continue;
    const Particle& pp = LAMBDAC.decayProducts()[ix].at(sign * PID::PROTON)[0];
    const Particles& K0 = LAMBDAC.decayProducts()[ix].at(310);
    if (mode == 0) {
      _h[0][0]->fill((pp.momentum() + K0[0].momentum()).mass2());
      _h[0][0]->fill((pp.momentum() + K0[1].momentum()).mass2());
      _h[0][1]->fill((K0[0].momentum() + K0[1].momentum()).mass2());
    }
    else {
      const Particle& eta = LAMBDAC.decayProducts()[ix].at(221)[0];
      _h[1][0]->fill((K0[0].momentum() + eta.momentum()).mass2());
      _h[1][1]->fill((pp.momentum() + K0[0].momentum()).mass2());
      _h[1][2]->fill((pp.momentum() + eta.momentum()).mass2());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix)
    for (unsigned int iy = 0; iy < 2 + ix; ++iy) normalize(_h[ix][iy], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2][3];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2022_I2160445);

} ```