Rivet analyses

Mass distributions in D_s⁺ → π⁺π⁺π⁻π⁰ decays

Experiment: BESIII (BEPC)

Inspire ID: 2801948

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 134 (2025) 1, 011904 - arXiv: 2406.17452

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⁻π⁰. 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_2024_I2801948.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
  class BESIII_2024_I2801948 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2801948);


    /// @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 (unsigned int ix = 0; ix < 7; ++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, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-211, 2}, {211, 1}, {111, 1}};
      DecayedParticles DS = apply<DecayedParticles>(event, "DS");
      // loop over particles
      for (unsigned int ix = 0; ix < DS.decaying().size(); ++ix) {
        int sign = 1;
        if (DS.decaying()[ix].pid() > 0 && DS.modeMatches(ix, 4, mode)) {
          sign = 1;
        }
        else if (DS.decaying()[ix].pid() < 0 && DS.modeMatches(ix, 4, modeCC)) {
          sign = -1;
        }
        else
          continue;
        const Particle& pi0 = DS.decayProducts()[ix].at(111)[0];
        const Particles& pip = DS.decayProducts()[ix].at(sign * 211);
        const Particle& pim = DS.decayProducts()[ix].at(-sign * 211)[0];
        double mpm[2];
        bool veto = false;
        for (unsigned int ix = 0; ix < 2; ++ix) {
          mpm[ix] = (pip[ix].momentum() + pim.momentum()).mass();
          if (mpm[ix] > 0.46 && mpm[ix] < 0.52) veto = true;
        }
        if (veto) continue;
        // eta veto
        double mpm0[2];
        for (unsigned int ix = 0; ix < 2; ++ix) {
          mpm0[ix] = (pip[ix].momentum() + pim.momentum() + pi0.momentum()).mass();
          if (mpm0[ix] > 0.52 && mpm0[ix] < 0.58) veto = true;
        }
        if (veto) continue;
        _h[0]->fill((pip[0].momentum() + pip[1].momentum()).mass());
        _h[1]->fill((pim.momentum() + pi0.momentum()).mass());
        _h[4]->fill((pip[0].momentum() + pip[1].momentum() + pim.momentum()).mass());
        _h[5]->fill((pip[0].momentum() + pip[1].momentum() + pi0.momentum()).mass());
        for (unsigned int ix = 0; ix < 2; ++ix) {
          _h[2]->fill(mpm[ix]);
          _h[3]->fill((pip[ix].momentum() + pi0.momentum()).mass());
          _h[6]->fill(mpm0[ix]);
        }
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[7];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2024_I2801948);

}

Rivet analyses

Mass distributions in Ds+ → π+π+π−π0 decays

Source code:BESIII_2024_I2801948.cc

Mass distributions in D_s⁺ → π⁺π⁺π⁻π⁰ decays

Source code:`BESIII_2024_I2801948.cc`