Rivet analyses

Mass distributions in D_s⁺ → π⁺π⁺π⁻π⁰π⁰ decays

Experiment: BESIII (BESIII)

Inspire ID: 2866208

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2501.04451

Beams: * *

Beam energies: ANY

Run details: - Any process producting D_s mesons, originally e+e-

Measurement of the mass distributions in the decay D_s⁺ → π⁺π⁺π⁻π⁰π⁰. The data were read from the plots in the paper. Resolution/acceptance effects have been not unfolded and given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:`BESIII_2025_I2866208.cc`

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

namespace Rivet {


  /// @brief D_s+ -> pi+ pi+ pi- pi0 pi0
  class BESIII_2025_I2866208 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2025_I2866208);


    /// @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);
      declare(DS, "DS");
      // histos
      for (size_t ix = 0; ix < 8; ++ix) {
        book(_h[ix], 1, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{211, 2}, {-211, 1}, {111, 2}};
      static const map<PdgId, unsigned int>& modeCC = {{-211, 2}, {211, 1}, {111, 2}};
      DecayedParticles DS = apply<DecayedParticles>(event, "DS");
      // loop over particles
      for (size_t id = 0; id < DS.decaying().size(); ++id) {
        int sign = 1;
        if (DS.decaying()[id].pid() > 0 && DS.modeMatches(id, 5, mode)) {
          sign = 1;
        }
        else if (DS.decaying()[id].pid() < 0 && DS.modeMatches(id, 5, modeCC)) {
          sign = -1;
        }
        else
          continue;
        const Particles& pi0 = DS.decayProducts()[id].at(111);
        const Particles& pip = DS.decayProducts()[id].at(sign * 211);
        const Particle& pim = DS.decayProducts()[id].at(-sign * 211)[0];
        double m0 = (pi0[0].mom() + pi0[1].mom()).mass();
        // K_S0 veto
        if (m0 > 0.487 && m0 < 0.511) continue;
        if (pip[0].parents()[0].pid() == PID::K0S || pip[1].parents()[0].pid() == PID::K0S
            || pim.parents()[0].pid() == PID::K0S)
          continue;
        // eta veto
        double mpm0[4];
        bool passCut = true;
        for (size_t ix = 0; ix < 2; ++ix) {
          for (size_t iy = 0; iy < 2; ++iy) {
            mpm0[2 * ix + iy] = (pi0[ix].mom() + pip[iy].mom() + pim.mom()).mass();
            if (mpm0[2 * ix + iy] > .49 && mpm0[2 * ix + iy] < .58) passCut = false;
          }
        }
        if (!passCut) continue;
        _h[0]->fill(m0);
        for (size_t ix = 0; ix < 4; ++ix) {
          _h[4]->fill(mpm0[ix] / GeV);
        }
        _h[5]->fill((pi0[0].mom() + pi0[1].mom() + pim.mom()).mass() / GeV);
        for (size_t ix = 0; ix < 2; ++ix) {
          _h[2]->fill((pip[ix].mom() + pim.mom()).mass() / GeV);
          _h[3]->fill((pi0[ix].mom() + pim.mom()).mass() / GeV);
          _h[6]->fill((pip[0].mom() + pip[1].mom() + pi0[ix].mom() + pim.mom()).mass() / GeV);
          _h[7]->fill((pi0[0].mom() + pi0[1].mom() + pip[ix].mom() + pim.mom()).mass() / GeV);
          for (size_t iy = 0; iy < 2; ++iy) {
            _h[1]->fill((pip[ix].mom() + pi0[iy].mom()).mass() / GeV);
          }
        }
      }
    }


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

    /// @}

    /// @name Histograms
    /// @{
    Histo1DPtr _h[8];
    /// @}
  };

  RIVET_DECLARE_PLUGIN(BESIII_2025_I2866208);
}

Rivet analyses

Mass distributions in Ds+ → π+π+π−π0π0 decays

Source code:BESIII_2025_I2866208.cc

Mass distributions in D_s⁺ → π⁺π⁺π⁻π⁰π⁰ decays

Source code:`BESIII_2025_I2866208.cc`