Rivet analyses

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

namespace Rivet {


  /// @brief B -> pi,rho l+ nu
  class BABAR_2011_I855306 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2011_I855306);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableParticles(Cuts::abspid == PID::BPLUS || Cuts::abspid == PID::B0), "UFS");
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_c[ix], "TMP/c_" + toString(ix + 1));
        for (unsigned int iy = 0; iy < 3; ++iy) {
          book(_h[ix][iy], ix + 1, 1, iy + 1);
        }
      }
    }

    // Calculate the Q2 using mother and daughter charged lepton
    double q2(const Particle& B, int mesonID) {
      FourMomentum q = B.mom() - select(B.children(), Cuts::pid == mesonID)[0];
      return q * q;
    }

    // Check for explicit decay into pdgids
    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
      // Trivial check to ignore any other decays but the one in question modulo photons
      const Particles children = mother.children(Cuts::pid != PID::PHOTON);
      if (children.size() != ids.size()) return false;
      // Check for the explicit decay
      return all(ids, [&](int i) { return count(children, hasPID(i)) == 1; });
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Get B+ Mesons
      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
        // B0 modes
        if (p.abspid() == 511) {
          _c[0]->fill();
          if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E})
              || isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
            double qq = q2(p, PID::PIMINUS);
            _h[0][0]->fill(qq);
            _h[0][2]->fill(qq);
          }
          else if (isSemileptonicDecay(p, {PID::PIPLUS, PID::ELECTRON, PID::NU_EBAR})
                   || isSemileptonicDecay(p, {PID::PIPLUS, PID::MUON, PID::NU_MUBAR})) {
            double qq = q2(p, PID::PIPLUS);
            _h[0][0]->fill(qq);
            _h[0][2]->fill(qq);
          }
          else if (isSemileptonicDecay(p, {PID::RHOMINUS, PID::POSITRON, PID::NU_E})
                   || isSemileptonicDecay(p, {PID::RHOMINUS, PID::ANTIMUON, PID::NU_MU})) {
            double qq = q2(p, PID::RHOMINUS);
            _h[1][0]->fill(qq);
            _h[1][2]->fill(qq);
          }
          else if (isSemileptonicDecay(p, {PID::RHOPLUS, PID::ELECTRON, PID::NU_EBAR})
                   || isSemileptonicDecay(p, {PID::RHOPLUS, PID::MUON, PID::NU_MUBAR})) {
            double qq = q2(p, PID::RHOPLUS);
            _h[1][0]->fill(qq);
            _h[1][2]->fill(qq);
          }
        }
        // B+ modes
        else {
          _c[1]->fill();
          if (isSemileptonicDecay(p, {PID::PI0, PID::POSITRON, PID::NU_E})
              || isSemileptonicDecay(p, {PID::PI0, PID::ANTIMUON, PID::NU_MU})
              || isSemileptonicDecay(p, {PID::PI0, PID::ELECTRON, PID::NU_EBAR})
              || isSemileptonicDecay(p, {PID::PI0, PID::MUON, PID::NU_MUBAR})) {
            _h[0][1]->fill(q2(p, PID::PI0));
          }
          else if (isSemileptonicDecay(p, {PID::RHO0, PID::POSITRON, PID::NU_E})
                   || isSemileptonicDecay(p, {PID::RHO0, PID::ANTIMUON, PID::NU_MU})
                   || isSemileptonicDecay(p, {PID::RHO0, PID::ELECTRON, PID::NU_EBAR})
                   || isSemileptonicDecay(p, {PID::RHO0, PID::MUON, PID::NU_MUBAR})) {
            _h[1][1]->fill(q2(p, PID::RHO0));
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // Br in units 10^-4 and average over e/mu modes
      for (unsigned int ix = 0; ix < 2; ++ix) {
        for (unsigned int iy = 0; iy < 3; ++iy) {
          if (iy == 1)
            scale(_h[ix][iy], 0.5 * 1e4 / *_c[1]);
          else
            scale(_h[ix][iy], 0.5 * 1e4 / *_c[0]);
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2][3];
    CounterPtr _c[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2011_I855306);

}