Rivet analyses

title: E791_2002_I585322

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

Experiment: E791 (Fermilab)

Inspire ID: 585322

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 89 (2002) 121801

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decay $D^+\to K^-\pi^+\pi^+$. 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:E791_2002_I585322.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D+ -> K-pi+pi+ class E791_2002_I585322 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(E791_2002_I585322);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 411);
  declare(ufs, "UFS");
  DecayedParticles DP(ufs);
  DP.addStable(PID::PI0);
  declare(DP, "DP");
  // histos
  book(_h_low, 1, 1, 1);
  book(_h_high, 1, 1, 2);
  book(_dalitz, "dalitz", 50, 0., 3.1, 50, 0.3, 3.1);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{211, 2}, {-321, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-211, 2}, {321, 1}};
  // Loop over D+ mesons
  DecayedParticles DP = apply<DecayedParticles>(event, "DP");
  for (unsigned int ix = 0; ix < DP.decaying().size(); ++ix) {
    int sign = 1;
    if (DP.modeMatches(ix, 3, mode))
      sign = 1;
    else if (DP.modeMatches(ix, 3, modeCC))
      sign = -1;
    else
      continue;
    const Particles& pip = DP.decayProducts()[ix].at(sign * 211);
    const Particle& Km = DP.decayProducts()[ix].at(-sign * 321)[0];
    double mplus = (Km.momentum() + pip[0].momentum()).mass2();
    double mminus = (Km.momentum() + pip[1].momentum()).mass2();
    if (mplus < mminus) swap(mplus, mminus);
    _h_low->fill(mminus);
    _h_high->fill(mplus);
    _dalitz->fill(mminus, mplus);
    _dalitz->fill(mplus, mminus);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_high, _h_low;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(E791_2002_I585322);

} ```