Rivet analyses

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

namespace Rivet {


  /// @brief B -> phi K pi
  class BABAR_2008_I792439 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I792439);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(333);
      B0.addStable(310);
      B0.addStable(111);
      declare(B0, "B0");
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_p[ix][0], 1, 2, 2 + ix);
        book(_p[ix][1], "TMP/norm_" + toString(ix));
        for (unsigned int iy = 0; iy < 2; ++iy) {
          book(_h_mass[ix][iy], 2, 1 + ix, 1 + iy);
          book(_h_angle[ix][iy], 3 + ix, 1, 1 + iy);
        }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{321, 1}, {-211, 1}, {333, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{-321, 1}, {211, 1}, {333, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{310, 1}, {111, 1}, {333, 1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
        int sign = 1, imode = -1;
        if (B0.modeMatches(ix, 3, mode1)) {
          imode = 0;
          sign = 1;
        }
        else if (B0.modeMatches(ix, 3, mode1CC)) {
          imode = 0;
          sign = -1;
        }
        else if (B0.modeMatches(ix, 3, mode2)) {
          imode = 1;
          sign = 1;
        }
        else
          continue;
        // particles
        const Particle& KK = B0.decayProducts()[ix].at(imode == 0 ? 321 * sign : 310)[0];
        const Particle& pi = B0.decayProducts()[ix].at(imode == 0 ? -211 * sign : 111)[0];
        const Particle& phi = B0.decayProducts()[ix].at(333)[0];
        // children of the phi
        if (phi.children().size() != 2) continue;
        if (phi.children()[0].abspid() != 321) continue;
        if (phi.children()[0].pid() != -phi.children()[1].pid()) continue;
        double mKpi = (KK.momentum() + pi.momentum()).mass();
        _h_mass[imode][0]->fill(mKpi);
        _h_mass[imode][1]->fill(phi.mass());
        Particle Kp1 = phi.children()[0];
        Particle Km1 = phi.children()[1];
        // B0 frame
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
            B0.decaying()[ix].momentum().betaVec());
        FourMomentum pKstar = boost1.transform(KK.momentum() + pi.momentum());
        FourMomentum pPhi = boost1.transform(phi.momentum());
        // K pi helicity angle
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
        FourMomentum pKp = boost2.transform(boost1.transform(KK.momentum()));
        Vector3 axis1 = pKstar.p3().unit();
        double cTheta1 = axis1.dot(pKp.p3().unit());
        // phi helicity angle
        LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
        FourMomentum pKp1 = boost3.transform(boost1.transform(Kp1.momentum()));
        Vector3 axis2 = pPhi.p3().unit();
        double cTheta2 = axis2.dot(pKp1.p3().unit());
        if (mKpi > .75 && mKpi < 1.05) {
          _h_angle[0][0]->fill(cTheta1);
          _h_angle[0][1]->fill(cTheta2);
          _p[0][0]->fill(-0.5 * (1 - 5. * sqr(cTheta2)));
          _p[0][1]->fill();
        }
        else if (mKpi > 1.13 && mKpi < 1.53) {
          _h_angle[1][0]->fill(cTheta1);
          _h_angle[1][1]->fill(cTheta2);
          _p[1][0]->fill(-0.5 * (1 - 5. * sqr(cTheta2)));
          _p[1][1]->fill();
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) {
        scale(_p[ix][0], 1. / *_p[ix][1]);
        for (unsigned int iy = 0; iy < 2; ++iy) {
          normalize(_h_mass[ix][iy], 1., false);
          normalize(_h_angle[ix][iy], 1., false);
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[2][2], _h_angle[2][2];
    CounterPtr _p[2][2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2008_I792439);

}