Rivet analyses

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

namespace Rivet {


  /// @brief B -> c l nu moments
  class BELLE_2021_I1917200 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2021_I1917200);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521), "UFS");
      // histos
      for (unsigned int il = 0; il < 2; ++il) {
        for (unsigned int ix = 0; ix < 4; ++ix) {
          book(_p[il][ix], 4 * il + 1 + ix, 1, 1);
        }
        for (unsigned int ix = 4; ix < 8; ++ix) {
          book(_p[il][ix], "TMP/p_" + toString(il) + "_" + toString(ix),
               refData<YODA::BinnedEstimate<string>>(4 * il + 1, 1, 1));
        }
      }
    }

    void findDecayProducts(const Particle& parent,
                           Particles& em,
                           Particles& ep,
                           Particles& nue,
                           Particles& nueBar,
                           bool& charm) {
      for (const Particle& p : parent.children()) {
        if (PID::isCharmHadron(p.pid())) {
          charm = true;
        }
        else if (p.pid() == PID::EMINUS || p.pid() == PID::MUON) {
          em.push_back(p);
        }
        else if (p.pid() == PID::EPLUS || p.pid() == PID::ANTIMUON) {
          ep.push_back(p);
        }
        else if (p.pid() == PID::NU_E || p.pid() == PID::NU_MU) {
          nue.push_back(p);
        }
        else if (p.pid() == PID::NU_EBAR || p.pid() == PID::NU_MUBAR) {
          nueBar.push_back(p);
        }
        else if (PID::isBottomHadron(p.pid())) {
          findDecayProducts(p, em, ep, nue, nueBar, charm);
        }
        else if (!PID::isHadron(p.pid())) {
          findDecayProducts(p, em, ep, nue, nueBar, charm);
        }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      if (_edges.empty()) _edges = _p[0][0]->xEdges();
      // find and loop over Upslion(4S)
      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
        if (p.children().empty() || (p.children().size() == 1 && p.children()[1].abspid() == p.abspid())) {
          continue;
        }
        // find decay products
        bool charm = false;
        Particles em, ep, nue, nueBar;
        findDecayProducts(p, em, ep, nue, nueBar, charm);
        if (!charm) continue;
        FourMomentum pl, pnu;
        unsigned int il = 0;
        if (em.size() == 1 && nueBar.size() == 1 && em[0].pid() + 1 == -nueBar[0].pid()) {
          pl = em[0].momentum();
          pnu = nueBar[0].momentum();
          if (em[0].abspid() == 13) il = 1;
        }
        else if (ep.size() == 1 && nue.size() == 1 && nue[0].pid() == -ep[0].pid() + 1) {
          pl = ep[0].momentum();
          pnu = nue[0].momentum();
          if (ep[0].abspid() == 13) il = 1;
        }
        else {
          continue;
        }
        double q2 = (pl + pnu).mass2();
        vector<double> q2n(8);
        for (unsigned int ix = 0; ix < 8; ++ix) q2n[ix] = pow(q2, 1 + ix);
        if (q2 < 3.0) continue;
        double q2cut = 3.0;
        for (unsigned int ibin = 0; ibin < 15; ++ibin) {
          if (q2 > q2cut) {
            for (unsigned int ix = 0; ix < 8; ++ix) {
              _p[il][ix]->fill(_edges[ibin], q2n[ix]);
            }
          }
          else {
            break;
          }
          q2cut += 0.5;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int il = 0; il < 2; ++il) {
        BinnedEstimatePtr<string> tmp[3];
        for (unsigned int ix = 0; ix < 3; ++ix) book(tmp[ix], 3 * il + 9 + ix, 1, 1);
        for (unsigned int iy = 0; iy < _p[il][0]->numBins(); ++iy) {
          const double N = _p[il][0]->bin(iy + 1).effNumEntries();
          double q2 = _p[il][0]->bin(iy + 1).mean(2), q4 = _p[il][1]->bin(iy + 1).mean(2),
                 q6 = _p[il][2]->bin(iy + 1).mean(2), q8 = _p[il][3]->bin(iy + 1).mean(2),
                 q10 = _p[il][4]->bin(iy + 1).mean(2), q12 = _p[il][5]->bin(iy + 1).mean(2),
                 q14 = _p[il][6]->bin(iy + 1).mean(2), q16 = _p[il][7]->bin(iy + 1).mean(2);
          // q4 case
          if (N <= 9) continue; // q8 needs 8 events + Bessel correction
          double value = q4 - sqr(q2);
          double error = (-sqr(q4) + 4 * sqr(q2) * (-sqr(q2) + 2 * q4) - 4 * q2 * q6 + q8) / N;
          tmp[0]->bin(iy + 1).set(value, sqrt(error));
          // q6 case
          if (N <= 13) continue; // q12 needs 12 events + Bessel correction
          value = q6 + q2 * (2 * sqr(q2) - 3 * q4);
          error = (q12 - sqr(q6) - 6 * q2 * (q10 - 5 * q4 * q6) + 3 * q4 * (3 * sqr(q4) - 2 * q8)
                   + sqr(q2) * (-72 * sqr(q4) + 36 * sqr(q2) * (-sqr(q2) + 3 * q4) - 48 * q2 * q6 + 21 * q8))
              / N;
          tmp[1]->bin(iy + 1).set(value, sqrt(error));
          // q8 case
          if (N <= 17) continue; // q16 needs 16 events + Bessel correction
          value = q8 + q2 * (-3 * q2 * sqr(q2) + 6 * q2 * q4 - 4 * q6);
          error = (q16 - 8 * q6 * (q10 - 2 * q4 * q6) - sqr(q8)
                   - 8 * q2 * (q14 - 3 * q4 * (q10 - 4 * q4 * q6) - 6 * q6 * q8)
                   + 4 * sqr(q2)
                       * (7 * q12 - 28 * sqr(q6) + 6 * q2 * (-3 * q10 + 22 * q4 * q6)
                          + 3 * q4 * (12 * sqr(q4) - 11 * q8)
                          + 3 * sqr(q2)
                              * (-12 * sqr(q2) * (sqr(q2) - 4 * q4) - 51 * sqr(q4) - 28 * q2 * q6 + 13 * q8)))
              / N;
          tmp[2]->bin(iy + 1).set(value, sqrt(error));
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedProfilePtr<string> _p[2][8];
    vector<string> _edges;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2021_I1917200);

}