Rivet analyses

Mass distributions in Λc+ → pKS0KS0 and Λc+ → pKS0η

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 Λc+ → pKS0KS0 and Λc+ → pKS0η 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++ -*-
#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);

}