Rivet analyses

title: E791_2001_I530319

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

Experiment: E791 (Fermilab)

Inspire ID: 530319

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 86 (2001) 765-769

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decay $D_s^+\to \pi^+\pi^+\pi^-$. 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_2001_I530319.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D_s+ -> pi+pi+pi- class E791_2001_I530319 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(E791_2001_I530319);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 431);
  declare(ufs, "UFS");
  DecayedParticles DS(ufs);
  DS.addStable(PID::PI0);
  DS.addStable(PID::K0S);
  declare(DS, "DS");
  // histos
  book(_h_pi, 1, 1, 1);
  book(_dalitz, "dalitz", 50, 0., 3.5, 50, 0.0, 3.5);
}

/// 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 DS = apply<DecayedParticles>(event, "DS");
  // loop over particles
  for (unsigned int ix = 0; ix < DS.decaying().size(); ++ix) {
    int sign = 1;
    if (DS.decaying()[ix].pid() > 0 && DS.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (DS.decaying()[ix].pid() < 0 && DS.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particles& pip = DS.decayProducts()[ix].at(sign * 211);
    const Particle& pim = DS.decayProducts()[ix].at(-sign * 211)[0];
    double m1 = (pim.momentum() + pip[0].momentum()).mass2();
    double m2 = (pim.momentum() + pip[1].momentum()).mass2();
    _h_pi->fill(m1);
    _h_pi->fill(m2);
    _dalitz->fill(m1, m2);
    _dalitz->fill(m2, m1);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pi;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(E791_2001_I530319);

} ```