Rivet analyses

title: BABAR_2008_I792597

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

Experiment: BABAR (PEP-II)

Inspire ID: 792597

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 79 (2009) 032003

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. Given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:BABAR_2008_I792597.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 BABAR_2008_I792597 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I792597);


/// @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_pippim[0], 1, 1, 3);
  book(_h_pippip, 1, 1, 4);
  book(_h_pippim[1], 1, 1, 1);
  book(_h_pippim[2], 1, 1, 2);
  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];
    // kinematic variables
    double x[3] = {(pim.momentum() + pip[0].momentum()).mass2(),
                   (pim.momentum() + pip[1].momentum()).mass2(),
                   (pip[0].momentum() + pip[1].momentum()).mass2()};
    if (x[0] > x[1]) swap(x[0], x[1]);
    _dalitz->fill(x[0], x[1]);
    _dalitz->fill(x[1], x[0]);
    // fill plots
    _h_pippim[0]->fill(x[0]);
    _h_pippim[0]->fill(x[1]);
    _h_pippim[1]->fill(x[0]);
    _h_pippim[2]->fill(x[1]);
    _h_pippip->fill(x[2]);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h_pippim[ix]);
  normalize(_h_pippip);
  normalize(_dalitz);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pippim[3], _h_pippip;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2008_I792597);

} ```