Rivet analyses

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

#define I_KNOW_THE_INITIAL_QUARKS_PROJECTION_IS_DODGY_BUT_NEED_TO_USE_IT
#include "Rivet/Projections/InitialQuarks.hh"

namespace Rivet {

  /// @brief B* production at LEP1
  class DELPHI_1995_I395026 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_1995_I395026);


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

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

      // // Initialise and register projections
      declare(Beam(), "Beams");
      declare(ChargedFinalState(), "FS");
      declare(InitialQuarks(), "IQF");
      declare(UnstableParticles(), "UFS");

      // Book histograms
      book(_h_ctheta1, 5, 1, 1);
      book(_h_ctheta2, "/TMP/ctheta", 20, -1., 1.);
      book(_h_z, 4, 1, 1);
      book(_c_hadron, "/TMP/chadron");
      book(_c_bottom, "/TMP/cbottom");
      book(_c_bStar, "/TMP/cbStar ");
      book(_c_B, "/TMP/cB     ");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // First, veto on leptonic events by requiring at least 4 charged FS particles
      const FinalState& fs = apply<FinalState>(event, "FS");
      const size_t numParticles = fs.particles().size();

      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
      if (numParticles < 2) {
        MSG_DEBUG("Failed leptonic event cut");
        vetoEvent;
      }
      MSG_DEBUG("Passed leptonic event cut");

      int flavour = 0;
      const InitialQuarks& iqf = apply<InitialQuarks>(event, "IQF");

      // If we only have two quarks (qqbar), just take the flavour.
      // If we have more than two quarks, look for the highest energetic q-qbar pair.
      if (iqf.particles().size() == 2) {
        flavour = iqf.particles().front().abspid();
      }
      else {
        map<int, double> quarkmap;
        for (const Particle& p : iqf.particles()) {
          if (quarkmap[p.pid()] < p.E()) {
            quarkmap[p.pid()] = p.E();
          }
        }
        double maxenergy = 0.;
        for (int i = 1; i <= 5; ++i) {
          if (quarkmap[i] + quarkmap[-i] > maxenergy) {
            flavour = i;
          }
        }
      }
      if (flavour == 5) _c_bottom->fill();
      _c_hadron->fill();
      // Get beams and average beam momentum
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      const double meanBeamMom = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0;
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);

      // loop over the particles
      for (const Particle& p : apply<UnstableParticles>(event, "UFS")
                                   .particles(Cuts::abspid == 513 or Cuts::abspid == 523
                                              or Cuts::abspid == 511 or Cuts::abspid == 521)) {
        int sign = p.pid() / p.abspid();
        // count number of Bs not from mixing or B*
        if (p.abspid() == 511 || p.abspid() == 521) {
          if (p.parents()[0].abspid() == p.abspid()) continue;
          if (p.parents()[0].abspid() == 513 || p.parents()[0].abspid() == 523) continue;
          _c_B->fill();
        }
        // B*
        else {
          _c_bStar->fill();
          double xE = p.momentum().t() / meanBeamMom;
          _h_z->fill(xE);
          Particle decay;
          if (p.children().size() != 2) continue;
          int mid = p.abspid() - 2;
          if (p.children()[0].pid() == sign * mid && p.children()[1].pid() == 22) {
            decay = p.children()[1];
          }
          else if (p.children()[1].pid() == sign * mid && p.children()[0].pid() == 22) {
            decay = p.children()[0];
          }
          else
            continue;
          LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
          Vector3 e1z = p.p3().unit();
          FourMomentum pp = boost.transform(decay.momentum());
          Vector3 axis1 = boost.transform(decay.momentum()).p3().unit();
          double ctheta = e1z.dot(axis1);
          _h_ctheta1->fill(ctheta);
          _h_ctheta2->fill(ctheta);
        }
      }
    }

    pair<double, double> calcRho(Histo1DPtr hist) {
      if (hist->numEntries() == 0.) return make_pair(0., 0.);
      double sum1(0.), sum2(0.);
      for (const auto& bin : hist->bins()) {
        double Oi = bin.sumW();
        if (Oi == 0.) continue;
        double ai = 0.125 * (-bin.xMin() * (3. + sqr(bin.xMin())) + bin.xMax() * (3. + sqr(bin.xMax())));
        double bi = 0.375 * (-bin.xMin() * (1. - sqr(bin.xMin())) + bin.xMax() * (1. - sqr(bin.xMax())));
        double Ei = bin.errW();
        sum1 += sqr(bi / Ei);
        sum2 += bi / sqr(Ei) * (Oi - ai);
      }
      return make_pair(sum2 / sum1, sqrt(1. / sum1));
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      // spectrum
      scale(_h_z, 1. / _c_hadron->val());
      // polarization
      scale(_h_ctheta1, 1. / _c_hadron->val());
      normalize(_h_ctheta2);
      pair<double, double> rho = calcRho(_h_ctheta2);
      BinnedEstimatePtr<string> h_rho;
      book(h_rho, 3, 1, 1);
      h_rho->bin(1).set(rho.first, rho.second);
      // no of B* per hadronic Z
      double val = _c_bStar->val() / _c_hadron->val();
      double err = val
          * sqrt(sqr(_c_bStar->err() / _c_bStar->val()) + sqr(_c_hadron->err() / _c_hadron->val()));
      BinnedEstimatePtr<string> h_nBS;
      book(h_nBS, 2, 1, 1);
      h_nBS->bin(1).set(val, err);
      // no of B* per b bbar
      val = _c_bStar->val() / _c_bottom->val();
      err = val * sqrt(sqr(_c_bStar->err() / _c_bStar->val()) + sqr(_c_bottom->err() / _c_bottom->val()));
      BinnedEstimatePtr<string> h1;
      book(h1, 1, 1, 1);
      h1->bin(1).set(val, err);
      Counter ctemp = *_c_bStar + *_c_B;
      // no of B*/B+B*
      val = _c_bStar->val() / ctemp.val();
      err = val * sqrt(sqr(_c_bStar->err() / _c_bStar->val()) + sqr(ctemp.err() / ctemp.val()));
      h1->bin(2).set(val, err);
      // average x_E
      val = _h_z->xMean();
      err = _h_z->xStdErr();
      h1->bin(3).set(val, err);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_ctheta1, _h_ctheta2, _h_z;
    CounterPtr _c_hadron, _c_bottom, _c_bStar, _c_B;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(DELPHI_1995_I395026);


}