Rivet analyses

Mass distributions in the decay τ− → π−KS0KS0

Experiment: BABAR (PEP-II)

Inspire ID: 1125567

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 86 (2012) 092013

Beams: * *

Beam energies: ANY

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

Measurements of mass distributions in τ− → π−KS0KS0 decays. The data were read from the plots in the paper and are not corrected, although the backgrounds given in the paper have been subtracted. The plots should therefore only be used for qualitative comparisons however the data is useful as there are not corrected distributions for this decay mode.

Source code:BABAR_2012_I1125567.cc

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

namespace Rivet {


  /// @brief tau -> pi- KS0 KS0 nu
  class BABAR_2012_I1125567 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1125567);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==15);
      declare(ufs, "UFS");
      DecayedParticles TAU(ufs);
      TAU.addStable(310);
      TAU.addStable(111);
      declare(TAU, "TAU");
      // histograms
      for(unsigned int ix=0;ix<3;++ix) {
    book(_h[ix],1,1,1+ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 310,2}, {-211,1},{ 16,1}};
      static const map<PdgId,unsigned int> & modeCC = { { 310,2}, { 211,1},{-16,1}};
      DecayedParticles TAU = apply<DecayedParticles>(event, "TAU");
      // loop over particles
      for(unsigned int ix=0;ix<TAU.decaying().size();++ix) {
        int sign = 1;
        if(TAU.decaying()[ix].pid()>0 &&
           TAU.modeMatches(ix,4,mode)) sign=1;
        else if (TAU.decaying()[ix].pid()<0 &&
             TAU.modeMatches(ix,4,modeCC)) sign=-1;
        else
          continue;
        const Particle  & pim = TAU.decayProducts()[ix].at(-211*sign)[0];
        const Particles & K0  = TAU.decayProducts()[ix].at( 310);
    _h[0]->fill((pim.momentum()+K0[0].momentum()+K0[1].momentum()).mass());
        _h[2]->fill((K0[0].momentum()+K0[1].momentum()).mass());
        for(unsigned int ix=0;ix<2;++ix) {
          _h[1]->fill((pim.momentum()+K0[ix].momentum()).mass());
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<3;++ix) {
    normalize(_h[ix],1.,false);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2012_I1125567);

}