Rivet analyses

3π mass distribution in τ− → π−π−π+ντ decays

Experiment: ARGUS (DORIS)

Inspire ID: 339268

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Z.Phys.C 58 (1993) 61-70

Beams: * *

Beam energies: ANY

Run details: - Any process producing tau leptons, originally e+e- > tau+tau-

Three pion mass distrubution in τ− → π−π−π+ντ decays. Data take from the tables in the paper.

Source code:ARGUS_1992_I339268.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief tau -> 3 pi
  class ARGUS_1992_I339268 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1992_I339268);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs(Cuts::abspid == 15);
      declare(ufs, "UFS");
      DecayedParticles TAU(ufs);
      TAU.addStable(310);
      TAU.addStable(111);
      declare(TAU, "TAU");
      // histos
      book(_h_mass, 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles TAU = apply<DecayedParticles>(event, "TAU");
      // loop over particles
      for (unsigned int ix = 0; ix < TAU.decaying().size(); ++ix) {
        int sign = TAU.decaying()[ix].pid() > 0 ? 1 : -1;
        if (!(TAU.modeMatches(ix, 4, mode) || TAU.modeMatches(ix, 4, modeCC))) {
          continue;
        }
        const Particles& pip = TAU.decayProducts()[ix].at(211 * sign);
        const Particles& pim = TAU.decayProducts()[ix].at(-211 * sign);
        double Q2 = (pip[0].mom() + pim[0].mom() + pim[1].mom()).mass2();
        _h_mass->fill(sqrt(Q2));
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_mass, 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass;
    const map<PdgId, unsigned int> mode = {{-211, 2}, {211, 1}, {16, 1}};
    const map<PdgId, unsigned int> modeCC = {{211, 2}, {-211, 1}, {-16, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ARGUS_1992_I339268);

}