Rivet analyses

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

namespace Rivet {


  /// @brief D*+/- polarization at 29 GeV
  class HRS_1987_I250823 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(HRS_1987_I250823);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(Beam(), "Beams");
      declare(Sphericity(FinalState()), "Sphericity");
      declare(UnstableParticles(), "UFS");
      for (unsigned int i = 0; i < 9; ++i) {
        unsigned int ix(0), iy(1);
        if (i < 3) {
          ix = 1;
          iy = i + 1;
        }
        else if (i == 3) {
          ix = 2;
        }
        else if (i < 6) {
          ix = 3;
          iy = i - 3;
        }
        else {
          ix = i - 2;
        }
        book(_p_rho00[i], ix, iy, 1);
        book(_p_rho11[i], ix, iy, 2);
        book(_p_rho10[i], ix, iy, 3);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // 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);
      Vector3 axis;
      if (beams.first.pid() > 0)
        axis = beams.first.momentum().p3().unit();
      else
        axis = beams.second.momentum().p3().unit();

      // sphericity, to define an axis
      const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");

      // loop over the particles
      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid == 413)) {
        int sign = p.pid() / p.abspid();
        Particle decay;
        double xE = p.momentum().E() / meanBeamMom;
        if (p.children()[0].pid() == sign * 421 && p.children()[1].pid() == sign * 211) {
          decay = p.children()[1];
        }
        else if (p.children()[1].pid() == sign * 421 && p.children()[0].pid() == sign * 211) {
          decay = p.children()[0];
        }
        else
          continue;
        // axis and ctheta
        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);
        // y and z axis
        Vector3 e1y = e1z.cross(axis).unit();
        Vector3 e1x = e1y.cross(e1z).unit();
        double phi = atan2(e1y.dot(axis1), e1x.dot(axis1));
        double w1 = 0.5 * (5. * sqr(ctheta) - 1.);
        double w2 = -1.25 * (1. - sqr(ctheta)) * cos(2. * phi);
        double w3 = -1.25 * sqrt(2) * ctheta * sqrt(1. - sqr(ctheta)) * cos(phi);
        // fill the hists by x_E
        for (unsigned int ix = 0; ix < 6; ++ix) {
          _p_rho00[ix]->fill(xE, w1);
          _p_rho11[ix]->fill(xE, w2);
          _p_rho10[ix]->fill(xE, w3);
        }
        _p_rho00[6]->fill(1., w1);
        _p_rho11[6]->fill(1., w2);
        _p_rho10[6]->fill(1., w3);
        // using jet axis
        double pT = sqrt(sqr(sphericity.sphericityMajorAxis().dot(p.momentum().p3()))
                         + sqr(sphericity.sphericityMinorAxis().dot(p.momentum().p3())));
        Vector3 axis2;
        if (p.momentum().p3().dot(sphericity.sphericityAxis()) >= 0.) {
          axis2 = sphericity.sphericityAxis();
        }
        else {
          axis2 = -sphericity.sphericityAxis();
        }
        Vector3 e2y = e1z.cross(axis2).unit();
        Vector3 e2x = e2y.cross(e1z).unit();
        // alpha and beta
        phi = atan2(e2y.dot(axis1), e2x.dot(axis1));
        w1 = 0.5 * (5. * sqr(ctheta) - 1.);
        w2 = -1.25 * (1. - sqr(ctheta)) * cos(2. * phi);
        w3 = -1.25 * sqrt(2) * ctheta * sqrt(1. - sqr(ctheta)) * cos(phi);
        if (xE < 0.4) continue;
        _p_rho00[7]->fill(1., w1);
        _p_rho11[7]->fill(1., w2);
        _p_rho10[7]->fill(1., w3);
        if (pT < 0.75) {
          _p_rho00[7]->fill(2., w1);
          _p_rho11[7]->fill(2., w2);
          _p_rho10[7]->fill(2., w3);
        }
        else {
          _p_rho00[7]->fill(3., w1);
          _p_rho11[7]->fill(3., w2);
          _p_rho10[7]->fill(3., w3);
        }
        if (sphericity.sphericity() >= 0.1) {
          _p_rho00[8]->fill(1., w1);
          _p_rho11[8]->fill(1., w2);
          _p_rho10[8]->fill(1., w3);
        }
        else {
          _p_rho00[8]->fill(2., w1);
          _p_rho11[8]->fill(2., w2);
          _p_rho10[8]->fill(2., w3);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() { }

    /// @}


    /// @name Histograms
    /// @{
    Profile1DPtr _p_rho00[9], _p_rho11[9], _p_rho10[9];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(HRS_1987_I250823);


}