Rivet analyses

Dalitz plot analysis of D+ → π+π+π−

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+ → π+π+π−. 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++ -*-
#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);

}