Rivet analyses

title: CLEOC_2007_I749602

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

Experiment: CLEOC (CESR)

Inspire ID: 749602

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 76 (2007) 012001

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decay $D^+\to \pi^+\pi^+\pi^-$. 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:CLEOC_2007_I749602.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D+ -> pi+pi+pi- class CLEOC_2007_I749602 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2007_I749602);


/// @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);
  DP.addStable(PID::K0S);
  DP.addStable(PID::ETA);
  DP.addStable(PID::ETAPRIME);
  declare(DP, "DP");
  // histos
  book(_h_pippim, 1, 1, 1);
  book(_h_pippip, 1, 1, 2);
  book(_dalitz, "dalitz", 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, 1}, {-211, 2}};
  DecayedParticles DP = apply<DecayedParticles>(event, "DP");
  // loop over particles
  for (unsigned int ix = 0; ix < DP.decaying().size(); ++ix) {
    int sign = 1;
    if (DP.decaying()[ix].pid() > 0 && DP.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (DP.decaying()[ix].pid() < 0 && DP.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particles& pip = DP.decayProducts()[ix].at(sign * 211);
    const Particles& pim = DP.decayProducts()[ix].at(-sign * 211);
    double m1 = (pim[0].momentum() + pip[0].momentum()).mass2();
    double m2 = (pim[0].momentum() + pip[1].momentum()).mass2();
    double m3 = (pip[0].momentum() + pip[1].momentum()).mass2();
    if (m1 > m2) swap(m1, m2);
    _dalitz->fill(m1, m2);
    // K_S0 veto
    if (m1 < 0.2 || m1 > 0.3) {
      _h_pippim->fill(m1);
      _h_pippim->fill(m2);
      _h_pippip->fill(m3);
    }
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(CLEOC_2007_I749602);

} ```