Rivet analyses

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

namespace Rivet {


  /// @brief Add a short analysis description here
  class ALEPH_2014_I1267648 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ALEPH_2014_I1267648);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableParticles(), "UFS");

      // Book histograms
      for (unsigned int ix = 0; ix < 5; ++ix)
        book(_h[ix], "TMP/h_" + toString(ix + 1), refData(1 + ix, 1, 1));
      book(_c, "TMP/ntau");
    }


    void findDecayProducts(const Particle& mother,
                           const int isign,
                           unsigned int& nstable,
                           unsigned int& npip,
                           unsigned int& npim,
                           unsigned int& npi0,
                           FourMomentum& ptot) {
      for (const Particle& p : mother.children()) {
        int id = p.pid();
        if (id == PID::KPLUS || id == PID::KMINUS) {
          ++nstable;
          ptot += p.momentum();
        }
        else if (id * isign == PID::PIPLUS) {
          ++npip;
          ++nstable;
          ptot += p.momentum();
        }
        else if (id * isign == PID::PIMINUS) {
          ++npim;
          ++nstable;
          ptot += p.momentum();
        }
        else if (id == PID::PI0) {
          ++nstable;
          ++npi0;
          ptot += p.momentum();
        }
        else if (id == PID::PHOTON)
          continue;
        else if (!p.children().empty())
          findDecayProducts(p, isign, nstable, npip, npim, npi0, ptot);
        else
          ++nstable;
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // Loop over taus
      for (const Particle& tau : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid == PID::TAU)) {
        _c->fill();
        FourMomentum ptot;
        unsigned int nstable(0), npip(0), npim(0), npi0(0);
        findDecayProducts(tau, tau.pid() / tau.abspid(), nstable, npip, npim, npi0, ptot);
        // tau -> pi pi0 nu_tau (both charges)
        if (npim == 1 && npi0 == 1 && nstable == 3) _h[0]->fill(ptot.mass2());
        // tau -> pi pi0 pi0 nu_tau (both charges)
        else if (npim == 1 && npi0 == 2 && nstable == 4)
          _h[1]->fill(ptot.mass2());
        //    tau -> pi pi0 pi0 pi0         (3,1,1)
        else if (npim == 1 && npi0 == 3 && nstable == 5)
          _h[2]->fill(ptot.mass2());
        //    tau -> 3 charged pions        (4,1,1)
        else if (npim == 2 && npip == 1 && nstable == 4)
          _h[3]->fill(ptot.mass2());
        //    tau -> 3 charged pions + pi0  (5,1,1)
        else if (npim == 2 && npip == 1 && npi0 == 1 && nstable == 5)
          _h[4]->fill(ptot.mass2());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 5; ++ix) {
        scale(_h[ix], 100. / *_c);
        Estimate1DPtr tmp;
        book(tmp, 1 + ix, 1, 1);
        barchart(_h[ix], tmp);
      }
    }

    /// @}


  private:


    /// @name Histograms
    /// @{
    Histo1DPtr _h[5];
    CounterPtr _c;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ALEPH_2014_I1267648);

}