Rivet analyses

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

namespace Rivet {


  /// @brief Lambda_c+ -> Lambda Kbar0 K+
  class BABAR_2006_I722213 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I722213);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 4122);
      declare(ufs, "UFS");
      DecayedParticles LAMBDAC(ufs);
      LAMBDAC.addStable(PID::PI0);
      LAMBDAC.addStable(PID::K0S);
      LAMBDAC.addStable(PID::ETA);
      LAMBDAC.addStable(PID::LAMBDA);
      LAMBDAC.addStable(-PID::LAMBDA);
      declare(LAMBDAC, "LAMBDAC");
      // histograms
      for (size_t ix = 0; ix < 3; ++ix) {
        book(_h_mass[ix], 1, 1, 1 + ix);
      }
      for (size_t ix = 0; ix < 2; ++ix) {
        book(_h_ctheta[ix], 2, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{PID::LAMBDA, 1}, {321, 1}, {310, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-PID::LAMBDA, 1}, {-321, 1}, {310, 1}};
      DecayedParticles LAMBDAC = apply<DecayedParticles>(event, "LAMBDAC");
      // loop over particles
      for (size_t ix = 0; ix < LAMBDAC.decaying().size(); ++ix) {
        int sign = 1;
        if (LAMBDAC.decaying()[ix].pid() > 0 && LAMBDAC.modeMatches(ix, 3, mode)) {
          sign = 1;
        }
        else if (LAMBDAC.decaying()[ix].pid() < 0 && LAMBDAC.modeMatches(ix, 3, modeCC)) {
          sign = -1;
        }
        else {
          continue;
        }
        const Particle& lam = LAMBDAC.decayProducts()[ix].at(sign * PID::LAMBDA)[0];
        const Particle& K0 = LAMBDAC.decayProducts()[ix].at(310)[0];
        const Particle& Kp = LAMBDAC.decayProducts()[ix].at(sign * 321)[0];
        double mLamK = (lam.mom() + K0.mom()).mass();
        _h_mass[0]->fill(mLamK);
        _h_mass[1]->fill((Kp.mom() + K0.mom()).mass() - Kp.mass() - K0.mass());
        _h_mass[2]->fill((lam.mom() + Kp.mom()).mass() - Kp.mass() - lam.mass());
        // take Xi(1690) to be any resonance in mass region
        if (mLamK < 1.6725 || mLamK > 1.6975) continue;
        if (LAMBDAC.decaying()[ix].children().size() != 2) continue;
        if (LAMBDAC.decaying()[ix].children()[0].abspid() != 321
            && LAMBDAC.decaying()[ix].children()[1].abspid() != 321)
          continue;
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
            LAMBDAC.decaying()[ix].mom().betaVec());
        FourMomentum pbaryon1 = boost1.transform(LAMBDAC.decaying()[ix].mom());
        FourMomentum pbaryon2 = boost1.transform(lam.mom());
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pbaryon1.betaVec());
        Vector3 axis = pbaryon1.p3().unit();
        FourMomentum pp = boost2.transform(pbaryon2);
        // calculate angle
        double cTheta = pp.p3().unit().dot(axis);
        _h_ctheta[0]->fill(cTheta);
        _h_ctheta[1]->fill(cTheta);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_mass);
      normalize(_h_ctheta);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[3];
    Histo1DPtr _h_ctheta[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2006_I722213);

}