Rivet analyses

Mass distributions in J/ψ → Λ̄0π+Σ−, Λ̄0π−Σ+ decays

Experiment: BESIII (BEPC)

Inspire ID: 2670262

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 108 (2023) 11, 112012 - arXiv: 2306.10319

Beams: * *

Beam energies: ANY

Run details: - Any process producing J/psi, originally e+e-

Mass distributions in J/ψ → Λ̄0π+Σ−, Λ̄0π−Σ+ decays and charge conjugate decays. The data were read from the figures in the paper and the backgrounds given subtracted.

Source code:BESIII_2023_I2670262.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief
  class BESIII_2023_I2670262 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2670262);

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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 443);
      declare(ufs, "UFS");
      DecayedParticles psi(ufs);
      psi.addStable(PID::PI0);
      psi.addStable(PID::K0S);
      psi.addStable(3122);
      psi.addStable(-3122);
      psi.addStable(3112);
      psi.addStable(-3112);
      psi.addStable(3222);
      psi.addStable(-3222);
      declare(psi, "psi");
      for (unsigned int ix = 0; ix < 4; ++ix) {
        for (unsigned int iy = 0; iy < 3; ++iy) book(_h[ix][iy], 1 + ix, 1, 1 + iy);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles psi = apply<DecayedParticles>(event, "psi");
      // loop over particles
      for (unsigned int ix = 0; ix < psi.decaying().size(); ++ix) {
        int isgn, ipi, isig = 3112, imode;
        if (psi.modeMatches(ix, 3, mode1)) {
          isgn = -1;
          ipi = 1;
          imode = 0;
        }
        else if (psi.modeMatches(ix, 3, mode2)) {
          isgn = 1;
          ipi = -1;
          imode = 1;
        }
        else if (psi.modeMatches(ix, 3, mode3)) {
          isgn = -1;
          ipi = -1;
          isig = 3222;
          imode = 2;
        }
        else if (psi.modeMatches(ix, 3, mode4)) {
          isgn = 1;
          ipi = 1;
          isig = 3222;
          imode = 3;
        }
        else
          continue;
        const Particle& lam = psi.decayProducts()[ix].at(isgn * 3122)[0];
        const Particle& sig = psi.decayProducts()[ix].at(-isgn * isig)[0];
        const Particle& pi = psi.decayProducts()[ix].at(ipi * 211)[0];
        _h[imode][0]->fill((lam.mom() + pi.mom()).mass());
        _h[imode][1]->fill((sig.mom() + pi.mom()).mass());
        _h[imode][2]->fill((lam.mom() + sig.mom()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h);
    }

    /// @}

    /// @name Histograms
    /// @{
    Histo1DPtr _h[4][3];
    const map<PdgId, unsigned int> mode1 = {{-3122, 1}, {3112, 1}, {211, 1}};
    const map<PdgId, unsigned int> mode2 = {{3122, 1}, {-3112, 1}, {-211, 1}};
    const map<PdgId, unsigned int> mode3 = {{-3122, 1}, {3222, 1}, {-211, 1}};
    const map<PdgId, unsigned int> mode4 = {{3122, 1}, {-3222, 1}, {211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2023_I2670262);

}