Rivet analyses

title: FOCUS_2004_I663820

Mass distributions in the decay $D^0\to K^+K^-\pi^+\pi^-$

Experiment: FOCUS (Fermilab)

Inspire ID: 663820

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 610 (2005) 225-234

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of the mass distributions in the decay $D^0\to K^+K^-\pi^+\pi^-$ by FOCUS. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. It is also not clear that any resolution effects have been unfolded.

Source code:FOCUS_2004_I663820.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D0 -> K+ K- pi+ pi- class FOCUS_2004_I663820 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(FOCUS_2004_I663820);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 421);
  declare(ufs, "UFS");
  DecayedParticles D0(ufs);
  D0.addStable(PID::PI0);
  D0.addStable(PID::K0S);
  D0.addStable(PID::ETA);
  D0.addStable(PID::ETAPRIME);
  declare(D0, "D0");
  // histograms
  for (unsigned int ix = 0; ix < 4; ++ix) book(_h[ix], 1, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // define the decay mode
  static const map<PdgId, unsigned int>& mode = {{321, 1}, {-321, 1}, {211, 1}, {-211, 1}};
  DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
  // loop over particles
  for (unsigned int ix = 0; ix < D0.decaying().size(); ++ix) {
    if (!D0.modeMatches(ix, 4, mode)) continue;
    int sign = D0.decaying()[ix].pid() / 421;
    const Particles& Kp = D0.decayProducts()[ix].at(sign * 321);
    const Particles& Km = D0.decayProducts()[ix].at(-sign * 321);
    const Particles& pip = D0.decayProducts()[ix].at(sign * 211);
    const Particles& pim = D0.decayProducts()[ix].at(-sign * 211);
    _h[0]->fill((Kp[0].momentum() + Km[0].momentum()).mass());
    _h[1]->fill((pip[0].momentum() + pim[0].momentum()).mass());
    _h[2]->fill((Kp[0].momentum() + pim[0].momentum()).mass());
    _h[2]->fill((Km[0].momentum() + pip[0].momentum()).mass());
    _h[3]->fill((Kp[0].momentum() + pip[0].momentum()).mass());
    _h[3]->fill((Km[0].momentum() + pim[0].momentum()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 4; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[4];
/// @}

};

RIVET_DECLARE_PLUGIN(FOCUS_2004_I663820);

} ```