Rivet analyses

Mass distributions in τ− → 2π−π+3π0ντ, 3π−2π+ντ and 3π−2π+π0ντ

Experiment: BABAR (PEP-II)

Inspire ID: 1185407

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 86 (2012) 092010

Beams: * *

Beam energies: ANY

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

Measurement of mass distributions in τ− → 2π−π+3π0ντ, 3π−2π+ντ and 3π−2π+π0ντ. 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_I1185407.cc

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

namespace Rivet {


  /// @brief tau -> 5 and 5 pion final states
  class BABAR_2012_I1185407 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1185407);


    /// @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");
      // histogram
      for(unsigned int ix=0;ix<4;++ix) {
    book(_h_6pi[ix],3,1,1+ix);
    if(ix>2) continue;
    book(_h_3pi[ix],1,1,1+ix);
    book(_h_5pi[ix],2,1,1+ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode1   = { {-211,2}, { 211,1},{111,3},{ 16,1}};
      static const map<PdgId,unsigned int> & mode1CC = { { 211,2}, {-211,1},{111,3},{-16,1}};
      static const map<PdgId,unsigned int> & mode2   = { {-211,3}, { 211,2},{ 16,1}};
      static const map<PdgId,unsigned int> & mode2CC = { { 211,3}, {-211,2},{-16,1}};
      static const map<PdgId,unsigned int> & mode3   = { {-211,3}, { 211,2},{111,1},{ 16,1}};
      static const map<PdgId,unsigned int> & mode3CC = { { 211,3}, {-211,2},{111,1},{-16,1}};
      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;
    int imode=-1;
        if(TAU.modeMatches(ix,7,mode1  ) ||
       TAU.modeMatches(ix,7,mode1CC))      imode = 0;
    else if(TAU.modeMatches(ix,6,mode2  ) ||
        TAU.modeMatches(ix,6,mode2CC)) imode = 1;
    else if(TAU.modeMatches(ix,7,mode3  ) ||
        TAU.modeMatches(ix,7,mode3CC)) imode = 2;
    else continue;
        const Particles & pip = TAU.decayProducts()[ix].at( 211*sign);
    const Particles & pim = TAU.decayProducts()[ix].at(-211*sign);
    FourMomentum ptotal;
    for(unsigned int ix=0;ix<pim.size();++ix) ptotal +=pim[ix].momentum();
    for(unsigned int ix=0;ix<pip.size();++ix) ptotal +=pip[ix].momentum();
    if(imode==1) {
      _h_5pi[2]->fill(ptotal.mass());
      for(unsigned int ix=0;ix<pim.size();++ix) {
        _h_5pi[1]->fill((ptotal-pim[ix].momentum()).mass());
        for(unsigned int iy=0;iy<pip.size();++iy) {
          _h_5pi[0]->fill((pim[ix].momentum()+pip[iy].momentum()).mass());
        }
      }
    }
    else {
      const Particles  & pi0 = TAU.decayProducts()[ix].at(111);
      FourMomentum ppi0;
      for(unsigned int ix=0;ix<pi0.size();++ix) ppi0 +=pi0[ix].momentum();
      ptotal+=ppi0;
      if(imode==0 ) {
        _h_3pi[0]->fill(ppi0.mass());
        _h_3pi[2]->fill(ptotal.mass());
        for(unsigned int ix=0;ix<pim.size();++ix) {
          for(unsigned int iy=0;iy<pi0.size();++iy) {
        _h_3pi[1]->fill((pip[0].momentum()+pim[ix].momentum()+pi0[iy].momentum()).mass());
          }
        }       
      }
      else {
        _h_6pi[3]->fill(ptotal.mass());
        for(unsigned int ix=0;ix<pim.size();++ix) {
          _h_6pi[2]->fill((ptotal-pim[ix].momentum()).mass());
          for(unsigned int iy=0;iy<pip.size();++iy) {
        _h_6pi[0]->fill((pim[ix].momentum()+pip[iy].momentum()).mass());
        _h_6pi[1]->fill((pim[ix].momentum()+pip[iy].momentum()+pi0[0].momentum()).mass());
          }
        }
      }
    }
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<4;++ix) {
    normalize(_h_6pi[ix]);
    if(ix>2) continue;
    normalize(_h_3pi[ix]);
    normalize(_h_5pi[ix]);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_3pi[3],_h_5pi[3],_h_6pi[4];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2012_I1185407);

}