Rivet analyses

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

namespace Rivet {


  /// @brief Xi_c0 at 7 TeV
  class ALICE_2018_I1642729 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ALICE_2018_I1642729);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projection
      declare(UnstableParticles(Cuts::pid == 4132 || Cuts::pid == 421), "UFS");
      // histos
      book(_h_Xi_pT[0], 1, 1, 1);
      book(_h_Xi_pT[1], "TMP/pT_Xi", refData(2, 1, 1));
      book(_h_D0_pT, "TMP/pT_D0", refData(2, 1, 1));
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Final state of unstable particles to get particle spectra
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
        // no mixing
        if (p.children().size() == 1 || p.children()[0].abspid() == p.abspid()) continue;
        // rapidity cut
        if (p.absrap() > 0.5) continue;
        const double pT = p.perp();
        if (p.pid() == 421) {
          _h_D0_pT->fill(pT);
        }
        else {
          _h_Xi_pT[0]->fill(pT);
          _h_Xi_pT[1]->fill(pT);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      const double factor = crossSection() / microbarn / sumOfWeights();
      // from PDG value of Xi_x0-> Xi- pi+ and ALICe measurement of ratio to semileptonic
      const double br = 0.0197;
      for (unsigned int ix = 0; ix < 2; ++ix) {
        scale(_h_Xi_pT[ix], br * factor);
      }
      scale(_h_D0_pT, factor);
      Estimate1DPtr tmp;
      book(tmp, 2, 1, 1);
      divide(_h_Xi_pT[1], _h_D0_pT, tmp);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Xi_pT[2], _h_D0_pT;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ALICE_2018_I1642729);

}