Rivet analyses

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

namespace Rivet {


  /// @brief B-> p Lambdabar X decays
  class BELLE_2007_I748975 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I748975);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(PID::PI0);
      BB.addStable(3122);
      BB.addStable(-3122);
      declare(BB, "BB");
      // histos
      for (unsigned int iy = 0; iy < 3; ++iy) {
        book(_h_mass[iy], 1, 1, 1 + iy);
        book(_h_cosp[iy], 2, 1, 1 + iy);
        book(_h_alpha[iy][0], 3, 1, 1 + iy);
        book(_h_alpha[iy][1], "TMP/h_alpha_" + toString(1 + iy));
        book(_h_E[iy][0], 4, 1, 1 + iy);
        book(_h_E[iy][1], "TMP/h_E_" + toString(1 + iy));
      }
      for (unsigned int iy = 0; iy < 2; ++iy) {
        book(_c[iy], "TMP/c_" + toString(iy + 1));
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      // loop over particles
      for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
        int imode = 0, sign = 1, idOther = 22;
        if (BB.decaying()[ix].abspid() == 521) {
          _c[0]->fill();
          if (BB.modeMatches(ix, 3, mode1)) {
            imode = 0;
            sign = 1;
          }
          else if (BB.modeMatches(ix, 3, mode1CC)) {
            imode = 0;
            sign = -1;
          }
          else if (BB.modeMatches(ix, 3, mode2)) {
            imode = 1;
            sign = 1;
            idOther = 111;
          }
          else if (BB.modeMatches(ix, 3, mode2CC)) {
            imode = 1;
            sign = -1;
            idOther = 111;
          }
          else
            continue;
        }
        else {
          _c[1]->fill();
          if (BB.modeMatches(ix, 3, mode3)) {
            imode = 2;
            sign = 1;
            idOther = -211;
          }
          else if (BB.modeMatches(ix, 3, mode3CC)) {
            imode = 2;
            sign = -1;
            idOther = 211;
          }
          else
            continue;
        }
        const Particle& pp = BB.decayProducts()[ix].at(sign * 2212)[0];
        const Particle& lbar = BB.decayProducts()[ix].at(-sign * 3122)[0];
        const Particle& other = BB.decayProducts()[ix].at(idOther)[0];
        FourMomentum pbaryon = pp.mom() + lbar.mom();
        double mass = pbaryon.mass();
        _h_mass[imode]->fill(mass);
        // boost to B rest frame
        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
            BB.decaying()[ix].mom().betaVec());
        FourMomentum pLam = boost.transform(lbar.mom());
        pbaryon = boost.transform(pbaryon);
        FourMomentum pProton = boost.transform(pp.mom());
        _h_E[imode][0]->fill(pLam.E());
        _h_E[imode][1]->fill();
        if (mass < 2.8) {
          Vector3 axis = boost.transform(other.mom()).p3().unit();
          LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(pbaryon.betaVec());
          double cosp = axis.dot(boost1.transform(pProton).p3().unit());
          _h_cosp[imode]->fill(cosp);
        }
        // finally the alpha parameter
        // Lambda decay products
        if (lbar.children().size() != 2) continue;
        Particle pbar;
        if (lbar.children()[0].pid() == -2212 && lbar.children()[1].pid() == 211) {
          pbar = lbar.children()[0];
        }
        else if (lbar.children()[1].pid() == -sign * 2212 && lbar.children()[0].pid() == sign * 211) {
          pbar = lbar.children()[1];
        }
        else {
          continue;
        }
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pLam.betaVec());
        Vector3 axis1 = -boost2.transform(boost.transform(BB.decaying()[ix].mom())).p3().unit();
        Vector3 axis2 = -boost2.transform(boost.transform(pbar.mom())).p3().unit();
        double cTheta = axis1.dot(axis2);
        _h_alpha[imode][0]->fill(1.5 * cTheta);
        _h_alpha[imode][1]->fill();
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_cosp, 1.0, false);
      scale(_h_mass[0], 1e6 / *_c[0]);
      scale(_h_mass[1], 1e6 / *_c[0]);
      scale(_h_mass[2], 1e6 / *_c[1]);
      for (unsigned int ix = 0; ix < 3; ++ix) {
        scale(_h_alpha[ix][0], 1. / *_h_alpha[ix][1]);
        scale(_h_E[ix][0], 1. / *_h_E[ix][1]);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[3], _h_cosp[3];
    CounterPtr _h_alpha[3][2], _h_E[3][2];
    CounterPtr _c[2];
    const map<PdgId, unsigned int> mode1 = {{2212, 1}, {-3122, 1}, {22, 1}};
    const map<PdgId, unsigned int> mode1CC = {{-2212, 1}, {3122, 1}, {22, 1}};
    const map<PdgId, unsigned int> mode2 = {{2212, 1}, {-3122, 1}, {111, 1}};
    const map<PdgId, unsigned int> mode2CC = {{-2212, 1}, {3122, 1}, {111, 1}};
    const map<PdgId, unsigned int> mode3 = {{2212, 1}, {-3122, 1}, {-211, 1}};
    const map<PdgId, unsigned int> mode3CC = {{-2212, 1}, {3122, 1}, {211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2007_I748975);

}