Rivet analyses

Measurements of Semi-Leptonic Tau Decays into Three Charged Hadrons

Experiment: BaBar (PEP-II)

Inspire ID: 756323

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett.100:011801,2008 - arXiv: 0707.2981 - SLAC-R-936

Beams: * *

Beam energies: ANY

Run details: - Tau production, can be any process but original data was in e+e− at the Υ(4S) resonance, with CoM boosts of 8.0 GeV~(e−) and 3.5GeV(e+)

Measurement of tau decays to three charged hadrons using a data sample corresponding to an integrated luminosity of 342 fb−1 collected with the BABAR detector at the SLAC PEP-II electron-positron storage ring operating at a center-of-mass energy near 10.58 GeV. Can be run with any process producing tau leptons.’

Source code:BABAR_2007_I756323.cc

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

namespace Rivet {


  /// @brief BABAR tau lepton to three charged hadrons
  ///
  /// @author Peter Richardson
  class BABAR_2007_I756323 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I756323);


    void init() {
      declare(UnstableParticles(), "UFS");

      book(_hist_pipipi_pipipi, 1, 1, 1);
      book(_hist_pipipi_pipi, 2, 1, 1);
      book(_hist_Kpipi_Kpipi, 3, 1, 1);
      book(_hist_Kpipi_Kpi, 4, 1, 1);
      book(_hist_Kpipi_pipi, 5, 1, 1);
      book(_hist_KpiK_KpiK, 6, 1, 1);
      book(_hist_KpiK_KK, 7, 1, 1);
      book(_hist_KpiK_piK, 8, 1, 1);
      book(_hist_KKK_KKK, 9, 1, 1);
      book(_hist_KKK_KK, 10, 1, 1);

      book(_weight_total, "/TMP/weight_total");
      book(_weight_pipipi, "/TMP/weight_pipipi");
      book(_weight_Kpipi, "/TMP/weight_Kpipi");
      book(_weight_KpiK, "/TMP/weight_KpiK");
      book(_weight_KKK, "/TMP/weight_KKK");
    }


    void analyze(const Event& e) {
      // Find the taus
      Particles taus;
      for (const Particle& p : apply<UnstableParticles>(e, "UFS").particles(Cuts::pid == PID::TAU)) {
        _weight_total->fill();
        Particles pip, pim, Kp, Km;
        unsigned int nstable = 0;
        // Find the decay products we want
        findDecayProducts(p, nstable, pip, pim, Kp, Km);
        if (p.pid() < 0) {
          swap(pip, pim);
          swap(Kp, Km);
        }
        if (nstable != 4) continue;
        // pipipi
        if (pim.size() == 2 && pip.size() == 1) {
          _weight_pipipi->fill();
          _hist_pipipi_pipipi->fill((pip[0].momentum() + pim[0].momentum() + pim[1].momentum()).mass());
          _hist_pipipi_pipi->fill((pip[0].momentum() + pim[0].momentum()).mass());
          _hist_pipipi_pipi->fill((pip[0].momentum() + pim[1].momentum()).mass());
        }
        else if (pim.size() == 1 && pip.size() == 1 && Km.size() == 1) {
          _weight_Kpipi->fill();
          _hist_Kpipi_Kpipi->fill((pim[0].momentum() + pip[0].momentum() + Km[0].momentum()).mass());
          _hist_Kpipi_Kpi->fill((pip[0].momentum() + Km[0].momentum()).mass());
          _hist_Kpipi_pipi->fill((pim[0].momentum() + pip[0].momentum()).mass());
        }
        else if (Kp.size() == 1 && Km.size() == 1 && pim.size() == 1) {
          _weight_KpiK->fill();
          _hist_KpiK_KpiK->fill((Kp[0].momentum() + Km[0].momentum() + pim[0].momentum()).mass());
          _hist_KpiK_KK->fill((Kp[0].momentum() + Km[0].momentum()).mass());
          _hist_KpiK_piK->fill((Kp[0].momentum() + pim[0].momentum()).mass());
        }
        else if (Kp.size() == 1 && Km.size() == 2) {
          _weight_KKK->fill();
          _hist_KKK_KKK->fill((Kp[0].momentum() + Km[0].momentum() + Km[1].momentum()).mass());
          _hist_KKK_KK->fill((Kp[0].momentum() + Km[0].momentum()).mass());
          _hist_KKK_KK->fill((Kp[0].momentum() + Km[1].momentum()).mass());
        }
      }
    }


    void finalize() {
      normalize(_hist_pipipi_pipipi);
      normalize(_hist_pipipi_pipi);
      normalize(_hist_Kpipi_Kpipi);
      normalize(_hist_Kpipi_Kpi);
      normalize(_hist_Kpipi_pipi);
      normalize(_hist_KpiK_KpiK);
      normalize(_hist_KpiK_KK);
      normalize(_hist_KpiK_piK);
      normalize(_hist_KKK_KKK);
      normalize(_hist_KKK_KK);
      Estimate0DPtr tmp;
      book(tmp, 11, 1, 1);
      divide(*_weight_pipipi, *_weight_total, tmp);
      scale(tmp, 100.);
      book(tmp, 12, 1, 1);
      divide(*_weight_Kpipi, *_weight_total, tmp);
      scale(tmp, 100.);
      book(tmp, 13, 1, 1);
      divide(*_weight_KpiK, *_weight_total, tmp);
      scale(tmp, 100.);
      book(tmp, 14, 1, 1);
      divide(*_weight_KKK, *_weight_total, tmp);
      scale(tmp, 100.);
    }


  private:

    // Histograms
    Histo1DPtr _hist_pipipi_pipipi, _hist_pipipi_pipi;
    Histo1DPtr _hist_Kpipi_Kpipi, _hist_Kpipi_Kpi, _hist_Kpipi_pipi;
    Histo1DPtr _hist_KpiK_KpiK, _hist_KpiK_KK, _hist_KpiK_piK;
    Histo1DPtr _hist_KKK_KKK, _hist_KKK_KK;

    // Weights counters
    CounterPtr _weight_total, _weight_pipipi, _weight_Kpipi, _weight_KpiK, _weight_KKK;


    void findDecayProducts(const Particle& mother,
                           unsigned int& nstable,
                           Particles& pip,
                           Particles& pim,
                           Particles& Kp,
                           Particles& Km) {
      for (const Particle& p : mother.children()) {
        long id = p.pid();
        if (id == PID::PI0)
          ++nstable;
        else if (id == PID::K0S)
          ++nstable;
        else if (id == PID::PIPLUS) {
          pip.push_back(p);
          ++nstable;
        }
        else if (id == PID::PIMINUS) {
          pim.push_back(p);
          ++nstable;
        }
        else if (id == PID::KPLUS) {
          Kp.push_back(p);
          ++nstable;
        }
        else if (id == PID::KMINUS) {
          Km.push_back(p);
          ++nstable;
        }
        else if (!p.children().empty()) {
          findDecayProducts(p, nstable, pip, pim, Kp, Km);
        }
        else
          ++nstable;
      }
    }
  };


  RIVET_DECLARE_ALIASED_PLUGIN(BABAR_2007_I756323, BABAR_2007_S7266081);

}

Aliases: - BABAR_2007_S7266081