Rivet analyses

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/Thrust.hh"
#include "Rivet/Tools/Random.hh"

namespace Rivet {


  /// @brief azimuthal asymmetries in pipi
  class BABAR_2014_I1254862 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2014_I1254862);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      const FinalState fs;
      declare(fs, "FS");
      declare(Thrust(fs), "Thrust");
      declare(Beam(), "Beams");
      // declare the histos for the distributions
      string charge[3] = {"Like", "Opposite", "All"};
      unsigned int nbin = 20;
      for (unsigned int icharge = 0; icharge < 3; ++icharge) {
        for (unsigned int ibin1 = 0; ibin1 < 6; ++ibin1) {
          for (unsigned int ibin2 = 0; ibin2 < 6; ++ibin2) {
            book(_h_thrust[icharge][ibin1][ibin2],
                 "TMP/h_thrust_" + charge[icharge] + "_" + toString(ibin1 + 1) + "_" + toString(ibin2 + 1),
                 nbin, 0., M_PI);
            book(_h_hadron[icharge][ibin1][ibin2],
                 "TMP/h_hadron_" + charge[icharge] + "_" + toString(ibin1 + 1) + "_" + toString(ibin2 + 1),
                 nbin, 0., M_PI);
          }
        }
      }
    }

    unsigned int iBin(double z) {
      if (z < .2)
        return 0;
      else if (z < .3)
        return 1;
      else if (z < .4)
        return 2;
      else if (z < .5)
        return 3;
      else if (z < .7)
        return 4;
      else
        return 5;
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // get the axis, direction of incoming electron
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      Vector3 axis1;
      if (beams.first.pid() > 0) {
        axis1 = beams.first.momentum().p3().unit();
      }
      else {
        axis1 = beams.second.momentum().p3().unit();
      }
      // apply thrust cuts  T > 0.8
      Thrust thrust = apply<Thrust>(event, "Thrust");
      if (thrust.thrust() <= 0.8) vetoEvent;
      // construct x,y,z axes for thrust defn
      ThreeVector t_z = thrust.thrustAxis();
      ThreeVector t_x = (axis1 - t_z.dot(axis1) * t_z).unit();
      ThreeVector t_y = t_z.cross(t_x);
      // loop over the particles
      Particles charged = apply<FinalState>(event, "FS").particles(Cuts::abspid == PID::PIPLUS);
      for (unsigned int ix = 0; ix < charged.size(); ++ix) {
        // z and angle cut
        const double x1 = 2. * charged[ix].momentum().t() / sqrtS();
        if (x1 < 0.15 || x1 > .9) continue;
        double dot1 = t_z.dot(charged[ix].p3().unit());
        if (abs(dot1) < sqrt(0.5)) continue;
        for (unsigned int iy = ix + 1; iy < charged.size(); ++iy) {
          const double x2 = 2. * charged[iy].momentum().t() / sqrtS();
          // z and angle cut
          if (x2 < 0.15 || x2 > .9) continue;
          double dot2 = t_z.dot(charged[iy].p3().unit());
          if (abs(dot2) < sqrt(.5) || dot1 * dot2 > 0.) continue;
          Particle p1 = charged[ix], p2 = charged[iy];
          double z1(x1), z2(x2);
          // randomly order the particles
          if (rand01() < 0.5) {
            swap(p1, p2);
            swap(z1, z2);
          }
          // thrust def
          double phi12 = atan2(p1.p3().dot(t_y), p1.p3().dot(t_x))
              + atan2(p2.p3().dot(t_y), p2.p3().dot(t_x));
          if (phi12 > M_PI) phi12 -= 2 * M_PI;
          if (phi12 < -M_PI) phi12 += 2 * M_PI;
          if (phi12 < 0.) phi12 = -phi12;
          // hadron defn
          ThreeVector h_z = p2.p3().unit();
          ThreeVector h_x = (axis1 - h_z.dot(axis1) * h_z).unit();
          ThreeVector pt1 = p1.p3() - h_z.dot(p1.p3()) * h_z;
          double phi0 = pt1.angle(h_x);
          if (phi0 > M_PI) phi0 -= 2 * M_PI;
          if (phi0 < -M_PI) phi0 += 2 * M_PI;
          unsigned int ibin1 = iBin(z1);
          unsigned int ibin2 = iBin(z2);
          if (p1.pid() == p2.pid()) {
            _h_thrust[0][ibin1][ibin2]->fill(phi12);
            _h_hadron[0][ibin1][ibin2]->fill(phi0);
          }
          else {
            _h_thrust[1][ibin1][ibin2]->fill(phi12);
            _h_hadron[1][ibin1][ibin2]->fill(phi0);
          }
          _h_thrust[2][ibin1][ibin2]->fill(phi12);
          _h_hadron[2][ibin1][ibin2]->fill(phi0);
        }
      }
    }

    pair<double, double> calcAsymmetry(Estimate1DPtr hist, double fact = 1.) {
      double sum1(0.), sum2(0.);
      for (const auto& bin : hist->bins()) {
        double Oi = bin.val();
        if (Oi == 0. || std::isnan(Oi)) continue;
        double ai = 1.;
        double bi = (sin(fact * bin.xMax()) - sin(fact * bin.xMin())) / (bin.xMax() - bin.xMin()) / fact;
        double Ei = bin.errAvg();
        sum1 += sqr(bi / Ei);
        sum2 += bi / sqr(Ei) * (Oi - ai);
      }
      if (sum1 == 0.) return make_pair(0., 0.);
      return make_pair(sum2 / sum1 * 1e2, sqrt(1. / sum1) * 1e2);
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ibin1 = 0; ibin1 < 6; ++ibin1) {
        Estimate1DPtr hthrustUL, hhadronUL;
        book(hthrustUL, 1, 1 + ibin1, 1);
        book(hhadronUL, 1, 1 + ibin1, 2);
        Estimate1DPtr hthrustUC, hhadronUC;
        book(hthrustUC, 2, 1 + ibin1, 1);
        book(hhadronUC, 2, 1 + ibin1, 2);
        for (unsigned int ibin2 = 0; ibin2 < 6; ++ibin2) {
          for (unsigned int icharge = 0; icharge < 3; ++icharge) {
            normalize(_h_thrust[icharge][ibin1][ibin2]);
            normalize(_h_hadron[icharge][ibin1][ibin2]);
          }
          Estimate1DPtr htemp;
          book(htemp, "TMP/R_thrust_UL_" + toString(ibin1) + "_" + toString(ibin2),
               _h_thrust[0][ibin1][ibin2]->xEdges());
          // UL thrust
          divide(_h_thrust[1][ibin1][ibin2], _h_thrust[0][ibin1][ibin2], htemp);
          pair<double, double> asym = calcAsymmetry(htemp);
          hthrustUL->bin(ibin2 + 1).set(asym.first, asym.second);
          // UC thrust
          book(htemp, "TMP/R_thrust_UC_" + toString(ibin1) + "_" + toString(ibin2),
               _h_thrust[1][ibin1][ibin2]->xEdges());
          divide(_h_thrust[1][ibin1][ibin2], _h_thrust[2][ibin1][ibin2], htemp);
          asym = calcAsymmetry(htemp);
          hthrustUC->bin(ibin2 + 1).set(asym.first, asym.second);
          // UL hadron
          book(htemp, "TMP/R_hadron_UL_" + toString(ibin1) + "_" + toString(ibin2),
               _h_hadron[1][ibin1][ibin2]->xEdges());
          divide(_h_hadron[1][ibin1][ibin2], _h_hadron[0][ibin1][ibin2], htemp);
          asym = calcAsymmetry(htemp);
          hhadronUL->bin(ibin2 + 1).set(asym.first, asym.second);
          // UC hadron
          book(htemp, "TMP/R_hadron_UC_" + toString(ibin1) + "_" + toString(ibin2),
               _h_hadron[1][ibin1][ibin2]->xEdges());
          divide(_h_hadron[1][ibin1][ibin2], _h_hadron[2][ibin1][ibin2], htemp);
          asym = calcAsymmetry(htemp);
          hhadronUC->bin(ibin2 + 1).set(asym.first, asym.second);
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_thrust[3][6][6], _h_hadron[3][6][6];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2014_I1254862);

}