Rivet analyses

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

namespace Rivet {


  /// @brief B -> p Lambda D
  class BELLE_2015_I1392799 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2015_I1392799);


    /// @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(411);
      B0.addStable(-411);
      B0.addStable(413);
      B0.addStable(-413);
      B0.addStable(PID::LAMBDA);
      B0.addStable(-PID::LAMBDA);
      declare(B0, "B0");
      //histograms
      for (unsigned int ix = 0; ix < 2; ++ix) {
        for (unsigned int iy = 0; iy < 2; ++iy) {
          book(_h[ix][iy], 1 + ix, 1, 1 + iy);
        }
      }
      book(_nB, "/TMP/nb");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{2212, 1}, {-3122, 1}, {-411, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{-2212, 1}, {3122, 1}, {411, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{2212, 1}, {-3122, 1}, {-413, 1}};
      static const map<PdgId, unsigned int>& mode2CC = {{-2212, 1}, {3122, 1}, {413, 1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
        _nB->fill();
        int sign = 1, imode = 0;
        if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode1)) {
          imode = 0;
          sign = 1;
        }
        else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, mode1CC)) {
          imode = 0;
          sign = -1;
        }
        else if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode2)) {
          imode = 1;
          sign = 1;
        }
        else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, mode2CC)) {
          imode = 1;
          sign = -1;
        }
        else
          continue;
        int iD = imode == 0 ? 411 : 413;
        const Particle& pp = B0.decayProducts()[ix].at(sign * 2212)[0];
        const Particle& lam = B0.decayProducts()[ix].at(-sign * 3122)[0];
        const Particle& Dm = B0.decayProducts()[ix].at(-sign * iD)[0];
        _h[0][imode]->fill((lam.momentum() + pp.momentum()).mass());
        // first boost to B rest frame
        LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(
            B0.decaying()[ix].momentum().betaVec());
        FourMomentum ppp = boostB.transform(pp.momentum());
        FourMomentum plam = boostB.transform(lam.momentum());
        FourMomentum pDm = boostB.transform(Dm.momentum());
        LorentzTransform boostpLam = LorentzTransform::mkFrameTransformFromBeta((ppp + plam).betaVec());
        ppp = boostpLam.transform(ppp);
        pDm = boostpLam.transform(pDm);
        _h[1][imode]->fill(ppp.p3().unit().dot(pDm.p3().unit()));
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix) {
        double fact = ix == 0 ? 1e3 : 1e6;
        for (unsigned int iy = 0; iy < 2; ++iy) {
          scale(_h[ix][iy], fact / *_nB);
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2][2];
    CounterPtr _nB;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2015_I1392799);

}