Rivet analyses

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

namespace Rivet {


  /// @brief B -> rho pi
  class BELLE_2002_I589587 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2002_I589587);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(111);
      declare(BB, "BB");
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h_mass[ix], 1, 1, 1 + ix);
        book(_h_angle[ix], 2, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
        int sign = BB.decaying()[ix].pid() / BB.decaying()[ix].abspid();
        unsigned int imode = 0;
        if (BB.modeMatches(ix, 3, mode1))
          imode = 0;
        else if (sign == 1 && BB.modeMatches(ix, 3, mode2))
          imode = 1;
        else if (sign == -1 && BB.modeMatches(ix, 3, mode2CC))
          imode = 1;
        else
          continue;
        const Particles& pip = BB.decayProducts()[ix].at(sign * 211);
        const Particles& pim = BB.decayProducts()[ix].at(-sign * 211);
        bool pipiVeto = false;
        Particle pRho[2];
        double delta = 1e30;
        for (const Particle& p1 : pip) {
          for (const Particle& p2 : pim) {
            double mpipi = (p1.mom() + p2.mom()).mass();
            if (abs(mpipi - 1.86484) < 0.14 || abs(mpipi - 3.09690) < 0.07 || abs(mpipi - 3.68610) < 0.05) {
              pipiVeto = true;
              break;
            }
            if (abs(mpipi - .77) < delta) {
              delta = abs(mpipi - .77);
              pRho[0] = p1;
              pRho[1] = p2;
            }
          }
        }
        if (pipiVeto) continue;
        if (imode == 0) {
          const Particle& pi0 = BB.decayProducts()[ix].at(111)[0];
          delta = 1e30;
          for (const Particle& p1 : pip) {
            double mpipi = (p1.mom() + pi0.mom()).mass();
            if (abs(mpipi - 1.86966) < 0.05) {
              pipiVeto = true;
              break;
            }
            if (abs(mpipi - .77) < delta) {
              delta = abs(mpipi - .77);
              pRho[0] = p1;
              pRho[1] = pi0;
            }
          }
          if (pipiVeto) continue;
          for (const Particle& p1 : pim) {
            double mpipi = (p1.mom() + pi0.mom()).mass();
            if (abs(mpipi - 1.86966) < 0.05) {
              pipiVeto = true;
              break;
            }
            if (abs(mpipi - .77) < delta) {
              delta = abs(mpipi - .77);
              pRho[0] = p1;
              pRho[1] = pi0;
            }
          }
          if (pipiVeto) continue;
        }
        FourMomentum prho = pRho[0].mom() + pRho[1].mom();
        double mpipi = prho.mass();
        _h_mass[imode]->fill(mpipi);
        // check if we should compute helicty angle
        if (imode == 0 && (mpipi < .6 || mpipi > 0.95))
          continue;
        else if (imode == 1 && (mpipi < .62 || mpipi > 0.92))
          continue;
        // compute the helicity angle
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
            BB.decaying()[ix].mom().betaVec());
        prho = boost1.transform(prho);
        FourMomentum ppi = boost1.transform(pRho[0].mom());
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(prho.betaVec());
        ppi = boost2.transform(ppi);
        double cTheta = ppi.p3().unit().dot(prho.p3().unit());
        _h_angle[imode]->fill(cTheta);
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[2], _h_angle[2];
    const map<PdgId, unsigned int> mode1 = {{211, 1}, {-211, 1}, {111, 1}};
    const map<PdgId, unsigned int> mode2 = {{211, 2}, {-211, 1}};
    const map<PdgId, unsigned int> mode2CC = {{-211, 2}, {211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2002_I589587);

}