Rivet analyses

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

namespace Rivet {


  /// @brief B -> Xs l+l-
  class BABAR_2013_I1272843 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2013_I1272843);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(UnstableParticles(Cuts::abspid == 521 || Cuts::abspid == 511), "UFS");
      // Book histograms
      for (unsigned int ix = 0; ix < 2; ++ix) book(_p_A[ix], 1, 1 + ix, 4);
      for (unsigned int iy = 0; iy < 3; ++iy) {
        book(_h_mX[iy], 2, 1, 1 + iy);
        for (unsigned int ix = 0; ix < 2; ++ix) book(_h_q2[ix][iy], 1, 1 + ix, 1 + iy);
      }
      book(_nBottom, "TMP/BottomCounter");
    }

    void findDecayProducts(bool& charm,
                           const Particle& mother,
                           unsigned int& nK0,
                           unsigned int& nKp,
                           unsigned int& nKm,
                           Particles& lp,
                           Particles& lm) {
      for (const Particle& p : mother.children()) {
        int id = p.pid();
        if (PID::isCharmHadron(p.pid()))
          charm = true;
        else if (id == PID::POSITRON || id == PID::ANTIMUON)
          lp.push_back(p);
        else if (id == PID::ELECTRON || id == PID::MUON)
          lm.push_back(p);
        else if (id == PID::KPLUS)
          ++nKp;
        else if (id == PID::KMINUS)
          ++nKm;
        else if (id == PID::K0S)
          ++nK0;
        else if (id == PID::PI0 || id == PID::PIPLUS || id == PID::PIMINUS) {
          continue;
        }
        else if (!p.children().empty()) {
          findDecayProducts(charm, p, nK0, nKp, nKm, lp, lm);
        }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Loop over bottoms
      for (const Particle& bottom : apply<UnstableParticles>(event, "UFS").particles()) {
        // remove mixing entries etc
        if (bottom.children()[0].abspid() == bottom.abspid()) continue;
        _nBottom->fill();
        bool charm = false;
        Particles lp, lm;
        unsigned int nK0(0), nKp(0), nKm(0);
        findDecayProducts(charm, bottom, nK0, nKp, nKm, lp, lm);
        if (charm) continue;
        unsigned int nk = nKp - nKm + nK0;
        if (nk % 2 == 0) continue;
        if (lp.size() != 1 || lm.size() != 1 || lp[0].pid() != -lm[0].pid()) continue;
        FourMomentum pl = (lp[0].momentum() + lm[0].momentum());
        FourMomentum pX = bottom.momentum() - pl;
        double q2 = pl.mass2();
        double mX = pX.mass();
        if (lm[0].pid() == 11) {
          _h_q2[0][0]->fill(q2);
          _h_q2[1][0]->fill(q2);
          _h_mX[0]->fill(mX);
        }
        else {
          _h_q2[0][1]->fill(q2);
          _h_q2[1][1]->fill(q2);
          _h_mX[1]->fill(mX);
        }
        _h_q2[0][2]->fill(q2);
        _h_q2[1][2]->fill(q2);
        _h_mX[2]->fill(mX);
        // A_CP doesn't include charmonium regions
        if (q2 < 6.8 || (q2 > 10.1 && q2 < 12.9) || q2 > 14.2) {
          double wgt = bottom.pid() > 0 ? -1 : 1;
          _p_A[0]->fill(q2, wgt);
          _p_A[1]->fill(q2, wgt);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int iy = 0; iy < 3; ++iy) {
        scale(_h_mX[iy], 1e6 / *_nBottom);
        for (unsigned int ix = 0; ix < 2; ++ix) scale(_h_q2[ix][iy], 1e6 / *_nBottom);
      }
    }
    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_q2[2][3], _h_mX[3];
    Profile1DPtr _p_A[2];
    CounterPtr _nBottom;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2013_I1272843);

}