Rivet analyses

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

namespace Rivet {


  /// @brief Upsilon(2S) -> Upsilon(1S) pi+pi-
  class CLEOII_1998_I467642 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1998_I467642);


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

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

      // Initialise and register projections
      declare(UnstableParticles(), "UFS");
      book(_h_charged_ex, 1, 1, 1);
      book(_h_charged_inc, 2, 1, 1);
      book(_h_neutral_ex, 3, 1, 1);
      book(_h_lept_ctheta, 4, 1, 1);
      book(_h_lept_phi, 4, 1, 2);
      book(_h_piStar_ctheta, 5, 1, 1);
      book(_h_piStar_phi, 5, 1, 2);
      book(_h_pi_ctheta, 6, 1, 1);
      book(_h_pi_phi, 6, 1, 2);
    }

    void findDecayProducts(const Particle& mother,
                           unsigned int& nstable,
                           Particles& pip,
                           Particles& pim,
                           Particles& pi0,
                           Particles& onium) {
      for (const Particle& p : mother.children()) {
        int id = p.pid();
        if (id == PID::PIMINUS) {
          pim.push_back(p);
          ++nstable;
        }
        else if (id == PID::PIPLUS) {
          pip.push_back(p);
          ++nstable;
        }
        else if (id == PID::PI0) {
          pi0.push_back(p);
          ++nstable;
        }
        else if (abs(id) % 1000 == 443 || abs(id) % 1000 == 553) {
          onium.push_back(p);
          ++nstable;
        }
        else if (!p.children().empty()) {
          findDecayProducts(p, nstable, pip, pim, pi0, onium);
        }
        else
          ++nstable;
      }
    }

    void findLeptons(const Particle& mother, unsigned int& nstable, Particles& lp, Particles& lm) {
      for (const Particle& p : mother.children()) {
        int id = p.pid();
        if (id == 11 || id == 13) {
          lm.push_back(p);
          ++nstable;
        }
        else if (id == -11 || id == -13) {
          lp.push_back(p);
          ++nstable;
        }
        else if (!p.children().empty()) {
          findLeptons(p, nstable, lp, lm);
        }
        else
          ++nstable;
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // loop over unstable particles
      for (const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid == 100553)) {
        unsigned int nstable(0);
        Particles pip, pim, pi0, onium;
        findDecayProducts(ups, nstable, pip, pim, pi0, onium);
        // check for onium
        if (onium.size() != 1 || onium[0].pid() != 553 || nstable != 3) continue;
        //pi+pi-
        if (pip.size() == 1 && pim.size() == 1) {
          FourMomentum q = pip[0].momentum() + pim[0].momentum();
          _h_charged_ex->fill(q.mass() / GeV);
          _h_charged_inc->fill(q.mass() / GeV);
          // leptons from Upsilon(1S) decay
          nstable = 0;
          Particles lp, lm;
          findLeptons(onium[0], nstable, lp, lm);
          if (nstable == 2 && lp.size() == 1 && lm.size() == 1) {
            _h_lept_ctheta->fill(cos(lp[0].momentum().polarAngle()));
            _h_lept_phi->fill(lp[0].momentum().azimuthalAngle());
          }
          // pions in rest frame
          LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(q.betaVec());
          FourMomentum ppi = boost.transform(pip[0].momentum());
          Vector3 axis1 = q.p3().unit();
          Vector3 axis2 = Vector3(0., 0., 1.).cross(axis1).unit();
          Vector3 axis3 = axis1.cross(axis2).unit();
          _h_piStar_ctheta->fill(axis1.dot(ppi.p3().unit()));
          double phi = atan2(axis3.dot(ppi.p3().unit()), axis2.dot(ppi.p3().unit()));
          if (phi < 0.) phi += 2. * M_PI;
          _h_piStar_phi->fill(phi);
          // pions in lab frame
          _h_pi_ctheta->fill(cos(q.polarAngle()));
          _h_pi_phi->fill(q.azimuthalAngle());
        }
        // 2pi0
        else if (pi0.size() == 2) {
          FourMomentum q = pi0[0].momentum() + pi0[1].momentum();
          _h_neutral_ex->fill(q.mass() / GeV);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_charged_ex);
      normalize(_h_charged_inc);
      normalize(_h_neutral_ex);
      normalize(_h_lept_ctheta);
      normalize(_h_lept_phi);
      normalize(_h_piStar_ctheta);
      normalize(_h_piStar_phi);
      normalize(_h_pi_ctheta);
      normalize(_h_pi_phi);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_charged_ex, _h_charged_inc, _h_neutral_ex;
    Histo1DPtr _h_lept_ctheta, _h_lept_phi, _h_piStar_ctheta, _h_piStar_phi, _h_pi_ctheta, _h_pi_phi;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CLEOII_1998_I467642);

}