Rivet analyses

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

namespace Rivet {


  /// @brief B -> D**  l nu
  class BELLE_2008_I768236 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I768236);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(411);
      BB.addStable(-411);
      BB.addStable(421);
      BB.addStable(-421);
      BB.addStable(413);
      BB.addStable(-413);
      BB.addStable(423);
      BB.addStable(-423);
      BB.addStable(PID::PI0);
      declare(BB, "BB");
      // hists
      for (unsigned int ix = 0; ix < 4; ++ix) {
        book(_h_mass[ix], 1, 1, 1 + ix);
        if (ix == 3 || ix == 1) continue;
        book(_h_hel[ix], 2, 1, 1 + ix);
        book(_h_w[ix], 3, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int> mode1[4] = {{{-411, 1}, {211, 1}, {-11, 1}, {12, 1}},
                                                        {{411, 1}, {-211, 1}, {11, 1}, {-12, 1}},
                                                        {{-411, 1}, {211, 1}, {-13, 1}, {14, 1}},
                                                        {{411, 1}, {-211, 1}, {13, 1}, {-14, 1}}};
      static const map<PdgId, unsigned int> mode2[4] = {{{-413, 1}, {211, 1}, {-11, 1}, {12, 1}},
                                                        {{413, 1}, {-211, 1}, {11, 1}, {-12, 1}},
                                                        {{-413, 1}, {211, 1}, {-13, 1}, {14, 1}},
                                                        {{413, 1}, {-211, 1}, {13, 1}, {-14, 1}}};
      static const map<PdgId, unsigned int> mode3[4] = {{{-421, 1}, {-211, 1}, {-11, 1}, {12, 1}},
                                                        {{421, 1}, {211, 1}, {11, 1}, {-12, 1}},
                                                        {{-421, 1}, {-211, 1}, {-13, 1}, {14, 1}},
                                                        {{421, 1}, {211, 1}, {13, 1}, {-14, 1}}};
      static const map<PdgId, unsigned int> mode4[4] = {{{-423, 1}, {-211, 1}, {-11, 1}, {12, 1}},
                                                        {{423, 1}, {211, 1}, {11, 1}, {-12, 1}},
                                                        {{-423, 1}, {-211, 1}, {-13, 1}, {14, 1}},
                                                        {{423, 1}, {211, 1}, {13, 1}, {-14, 1}}};
      // loop over B mesons
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      // loop over particles
      for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
        for (unsigned int il = 0; il < 4; ++il) {
          int iD, imode = 0;
          if (BB.modeMatches(ix, 4, mode1[il])) {
            imode = 0;
            iD = 411;
          }
          else if (BB.modeMatches(ix, 4, mode2[il])) {
            imode = 1;
            iD = 413;
          }
          else if (BB.modeMatches(ix, 4, mode3[il])) {
            imode = 2;
            iD = 421;
          }
          else if (BB.modeMatches(ix, 4, mode4[il])) {
            imode = 3;
            iD = 423;
          }
          else
            continue;
          int sign = il % 2 == 0 ? 1 : -1;
          int ipi = -sign * 211;
          iD *= -sign;
          if (imode < 2) ipi *= -1;
          const Particle& pi1 = BB.decayProducts()[ix].at(ipi)[0];
          const Particle& DD = BB.decayProducts()[ix].at(iD)[0];
          FourMomentum pHad = pi1.mom() + DD.mom();
          double mass = pHad.mass();
          _h_mass[imode]->fill(mass);
          // just the D pi modes for helicty and w
          if (imode % 2 != 0) continue;
          // check ingtermediate
          int inter = -1;
          for (unsigned int iz = 0; iz < BB.decaying()[ix].children().size(); ++iz) {
            if (BB.decaying()[ix].children()[iz].abspid() == 10411
                || BB.decaying()[ix].children()[iz].abspid() == 10421) {
              inter = 0;
              break;
            }
            else if (BB.decaying()[ix].children()[iz].abspid() == 415
                     || BB.decaying()[ix].children()[iz].abspid() == 425) {
              inter = 2;
              break;
            }
          }
          if (inter < 0) continue;
          // First boost all relevant momenta into the B-rest frame
          const LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
              BB.decaying()[ix].mom().betaVec());
          // Momenta in B rest frame:
          FourMomentum pDSS = boost1.transform(pHad);
          FourMomentum pW = boost1.transform(BB.decaying()[ix].mom() - pHad);
          FourMomentum ppi = boost1.transform(pi1);
          const LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDSS.betaVec());
          double ctheta = pW.p3().unit().dot(boost2.transform(ppi).p3().unit());
          _h_hel[inter]->fill(abs(ctheta));
          double mB2 = BB.decaying()[ix].mom().mass2();
          double mD2 = sqr(mass);
          double w = (mB2 + mD2 - pW.mass2()) / (2. * sqrt(mB2) * sqrt(mD2));
          _h_w[inter]->fill(w);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_mass, 1.0, false);
      normalize(_h_hel, 1.0, false);
      normalize(_h_w, 1.0, false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[4], _h_hel[3], _h_w[3];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2008_I768236);

}