Rivet analyses

title: DELPHI_1999_I448370

Charged particle fragmentation functions at LEP1

Experiment: DELPHI (LEP)

Inspire ID: 448370

Status: VALIDATED

Authors: - Peter Richardson

References: - Eur.Phys.J. C6 (1999) 19-33

Beams: e+ e-

Beam energies: (45.6, 45.6)GeV

Run details: - e+e-> hadrons

The transverse, longitudinal and asymmetric components of the fragmentation function are measured from the inclusive charged particles produced in $e^+e^-$ collisions at LEP, include separation of bottom and light quark(uds) events.

Source code:DELPHI_1999_I448370.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

define I_KNOW_THE_INITIAL_QUARKS_PROJECTION_IS_DODGY_BUT_NEED_TO_USE_IT

include "Rivet/Projections/InitialQuarks.hh"

namespace Rivet {

/// @brief Add a short analysis description here class DELPHI_1999_I448370 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_1999_I448370);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "FS");
  declare(InitialQuarks(), "IQF");

  // Book histograms
  book(_h_F_T, 1, 1, 1);
  book(_h_F_L, 2, 1, 1);
  book(_h_F_A, 3, 1, 1);
  book(_h_F_TL, 4, 1, 1);
  book(_h_F_T_total, 5, 1, 1);
  book(_h_F_L_total, 5, 1, 2);
  book(_h_F_TL_total, 5, 1, 3);
  book(_h_b_F_T, 7, 1, 1);
  book(_h_b_F_L, 7, 1, 2);
  book(_h_light_F_T, 8, 1, 1);
  book(_h_light_F_L, 8, 1, 2);
  book(_n_bottom, 9, 1, 1);
  book(_n_light, 9, 1, 2);

  book(_c_light, "/TMP/wLight");
  book(_c_bottom, "/TMP/wBottom");
  book(_c_total, "/TMP/wTotal");
}


/// 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();
  else if (flavour != 4)
    _c_light->fill();
  _c_total->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);
  Vector3 axis;
  if (beams.first.pid() > 0) {
    axis = beams.first.momentum().p3().unit();
  }
  else {
    axis = beams.second.momentum().p3().unit();
  }

  // loop over charged particles
  double v = 0.8, v2 = sqr(v), v5 = v2 * v2 * v;
  for (const Particle& p : fs.particles()) {
    double xp = p.p3().mod() / meanBeamMom;
    double ctheta = axis.dot(p.momentum().p3().unit());
    if (abs(ctheta) < 0.8) {
      double WT = 0.5 / v5 * (5. * sqr(ctheta) * (3. - v2) - v2 * (5. - 3. * v2));
      double WL = 0.25 / v5 * (v2 * (5. + 3. * v2) - 5. * sqr(ctheta) * (3. + v2));
      double WA = 2. * ctheta / v2 / v;
      _h_F_T->fill(xp, WT);
      _h_F_L->fill(xp, WL);
      _h_F_TL->fill(xp, (WL + WT));
      _h_F_T_total->fill(xp, 0.5 * xp * WT);
      _h_F_L_total->fill(xp, 0.5 * xp * WL);
      _h_F_TL_total->fill(xp, 0.5 * xp * (WL + WT));
      if (p.charge() > 0) {
        _h_F_A->fill(xp, WA);
      }
      else {
        _h_F_A->fill(xp, -WA);
      }
      if (flavour == 5) {
        _h_b_F_T->fill(xp, WT);
        _h_b_F_L->fill(xp, WL);
      }
      else if (flavour != 4) {
        _h_light_F_T->fill(xp, WT);
        _h_light_F_L->fill(xp, WL);
      }
    }
  }

  if (flavour == 5) {
    _n_bottom->fill(Ecm, fs.particles().size());
  }
  else if (flavour != 4) {
    _n_light->fill(Ecm, fs.particles().size());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_F_T, 1. / *_c_total);
  scale(_h_F_L, 1. / *_c_total);
  scale(_h_F_A, 1. / *_c_total);
  scale(_h_F_TL, 1. / *_c_total);
  {
    Estimate1DPtr temp;
    divide(_h_F_L, _h_F_T, book(temp, 6, 1, 1));
  }
  {
    Estimate1DPtr temp;
    divide(_h_F_L, _h_F_TL, book(temp, 6, 1, 2));
  }
  scale(_h_F_T_total, 1. / *_c_total);
  scale(_h_F_L_total, 1. / *_c_total);
  scale(_h_F_TL_total, 1. / *_c_total);
  scale(_h_b_F_T, 1. / *_c_bottom);
  scale(_h_b_F_L, 1. / *_c_bottom);
  scale(_h_light_F_T, 1. / *_c_light);
  scale(_h_light_F_L, 1. / *_c_light);
  scale(_n_bottom, 1. / *_c_bottom);
  scale(_n_light, 1. / *_c_light);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_F_T, _h_F_L, _h_F_A, _h_F_TL, _h_b_F_T, _h_b_F_L, _h_light_F_T, _h_light_F_L;
Histo1DPtr _h_F_T_total, _h_F_L_total, _h_F_TL_total;
BinnedHistoPtr<string> _n_light, _n_bottom;
CounterPtr _c_light, _c_bottom, _c_total;
const string Ecm = "91.2";
/// @}

};

RIVET_DECLARE_PLUGIN(DELPHI_1999_I448370);

} ```