Rivet analyses

Dalitz plot analysis of D+ → K+K+K−

Experiment: LHCB (LHC)

Inspire ID: 1720423

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - JHEP 04 (2019) 063

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+ -> K+ K+ K-

Measurement of the mass distributions in the decay D+ → K+K+K−. The data were read extracted from the plots in the paper and the backgrounds subtracted. 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:LHCB_2019_I1720423.cc

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

namespace Rivet {


  /// @brief D+ -> K+K+K-
  class LHCB_2019_I1720423 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2019_I1720423);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(UnstableParticles(), "UFS");
      book(_h_KpKm[0], 1, 1, 1);
      book(_h_KpKp, 1, 1, 2);
      book(_h_KpKm[1], 1, 1, 3);
      book(_h_KpKm[2], 1, 1, 4);
      book(_dalitz, "dalitz", 50, 0.9, 1.8, 50, 1.1, 1.9);
    }

    void findDecayProducts(const Particle& mother, unsigned int& nstable, Particles& Kp, Particles& Km) {
      for (const Particle& p : mother.children()) {
        int id = p.pid();
        if (id == PID::PIPLUS || id == PID::PIMINUS || id == PID::K0S || id == PID::K0L || id == PID::PI0) {
          ++nstable;
        }
        else if (id == PID::KPLUS) {
          Kp.push_back(p);
          ++nstable;
        }
        else if (id == PID::KMINUS) {
          Km.push_back(p);
          ++nstable;
        }
        else if (!p.children().empty()) {
          findDecayProducts(p, nstable, Kp, Km);
        }
        else
          ++nstable;
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      for (const Particle& meson : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid == 411)) {
        unsigned int nstable(0);
        Particles Kp, Km;
        findDecayProducts(meson, nstable, Kp, Km);
        if (nstable != 3) continue;
        if (meson.pid() < 0) {
          swap(Km, Kp);
        }
        if (Km.size() == 1 && Kp.size() == 2) {
          double m1 = (Km[0].momentum() + Kp[0].momentum()).mass2();
          double m2 = (Km[0].momentum() + Kp[1].momentum()).mass2();
          double m3 = (Kp[0].momentum() + Kp[1].momentum()).mass2();
          if (m1 > m2) swap(m1, m2);
          _dalitz->fill(m1, m2);
          _h_KpKm[0]->fill(m1);
          _h_KpKm[0]->fill(m2);
          _h_KpKm[2]->fill(m1);
          _h_KpKm[1]->fill(m2);
          _h_KpKp->fill(m3);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h_KpKm[ix]);
      normalize(_h_KpKp);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_KpKm[3], _h_KpKp;
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(LHCB_2019_I1720423);

}