Rivet analyses

title: FOCUS_2003_I635446

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

Experiment: FOCUS (Fermilab)

Inspire ID: 635446

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 585 (2004) 200-212

Beams: * *

Beam energies: ANY

Run details: - Any process producing D_s+/D+ -> pi+ pi+ pi-

Measurement of the mass distributions in the decays $D_s^+$ and $D^+\to \pi^+\pi^+\pi^-$. The data were read 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:FOCUS_2003_I635446.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D_s+/D+ -> pi+pi+pi- class FOCUS_2003_I635446 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(FOCUS_2003_I635446);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 411 or Cuts::abspid == 431);
  declare(ufs, "UFS");
  DecayedParticles DD(ufs);
  DD.addStable(PID::PI0);
  DD.addStable(PID::K0S);
  declare(DD, "DD");
  // histos
  book(_h_pippim[0], 1, 1, 1);
  book(_h_pippim[1], 1, 1, 2);
  book(_h_pippim[2], 2, 1, 1);
  book(_h_pippim[3], 2, 1, 2);
  book(_dalitz[0], "dalitz1", 50, 0., 2.0, 50, 0.0, 3.5);
  book(_dalitz[1], "dalitz2", 50, 0., 1.8, 50, 0.0, 3.1);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{211, 2}, {-211, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-211, 2}, {211, 1}};
  DecayedParticles DD = apply<DecayedParticles>(event, "DD");
  // loop over particles
  for (unsigned int ix = 0; ix < DD.decaying().size(); ++ix) {
    int sign = 1;
    if (DD.decaying()[ix].pid() > 0 && DD.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (DD.decaying()[ix].pid() < 0 && DD.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particles& pip = DD.decayProducts()[ix].at(sign * 211);
    const Particle& pim = DD.decayProducts()[ix].at(-sign * 211)[0];
    double m1 = (pim.momentum() + pip[0].momentum()).mass2();
    double m2 = (pim.momentum() + pip[1].momentum()).mass2();
    if (m1 > m2) swap(m1, m2);
    if (DD.decaying()[ix].abspid() == 431) {
      _dalitz[0]->fill(m1, m2);
      _h_pippim[0]->fill(m1);
      _h_pippim[1]->fill(m2);
    }
    else {
      _dalitz[1]->fill(m1, m2);
      _h_pippim[2]->fill(m1);
      _h_pippim[3]->fill(m2);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix) {
    normalize(_dalitz[ix]);
    normalize(_h_pippim[ix]);
    normalize(_h_pippim[ix + 2]);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pippim[4];
Histo2DPtr _dalitz[2];
/// @}

};

RIVET_DECLARE_PLUGIN(FOCUS_2003_I635446);

} ```