Rivet analyses

title: LHCB_2019_I1720423

Dalitz plot analysis of $D^+\to K^+K^+K^-$

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 $D^+\to K^+K^+K^-$. 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++ // -- 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);

} ```