Rivet analyses

title: DELPHI_1995_I394052

$K^\pm$ and $p,\bar{p}$ spectra in hadronic $Z^0$ decays

Experiment: DELPHI (LEP)

Inspire ID: 394052

Status: VALIDATED

Authors: - Peter Richardson

References: - Nucl.Phys. B444 (1995) 3-26, 1995

Beams: e+ e-

Beam energies: (45.6, 45.6)GeV

Run details: - Hadronic Z decay events generated on the Z pole ($\sqrt{s} = 91.2$ GeV)

DELPHI results for the spectra for $K^\pm$ and $p,\bar{p}$ production in hadronic $Z^0$ decays.

Source code:DELPHI_1995_I394052.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief K+/- and protno spectra class DELPHI_1995_I394052 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_1995_I394052);


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

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

  // Book histograms
  book(_h_kaon_p, 3, 1, 1);
  book(_h_kaon_x, 5, 1, 1);
  book(_h_proton_p, 4, 1, 1);
  book(_h_proton_x, 6, 1, 1);

  _axis[0] = YODA::Axis<double>(
      {0.017543859649122806, 0.024122807017543862, 0.03070175438596491, 0.03728070175438596,
       0.043859649122807015, 0.05482456140350877, 0.06578947368421052, 0.07675438596491228,
       0.08771929824561403, 0.21929824561403508, 0.2631578947368421, 0.30701754385964913,
       0.3508771929824561, 0.39473684210526316, 0.43859649122807015, 0.5043859649122807});
  _axis[1] = YODA::Axis<double>({0.03070175438596491, 0.03728070175438596, 0.043859649122807015,
                                 0.05482456140350877, 0.06578947368421052, 0.07675438596491228,
                                 0.08771929824561403, 0.09868421052631579, 0.10964912280701754});
}


/// Perform the per-event analysis
void analyze(const Event& event) {

  if (_edges[0].empty()) _edges[0] = _h_kaon_x->xEdges();
  if (_edges[1].empty()) _edges[1] = _h_proton_x->xEdges();

  // 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");

  // 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);
  for (const Particle& p : fs.particles(Cuts::abspid == 321 or Cuts::abspid == 2212)) {
    double modp = p.p3().mod();
    double xp = modp / meanBeamMom;
    if (abs(p.pid()) == 321) {
      _h_kaon_p->fill(modp);
      _h_kaon_x->fill(map2string(xp, 0));
    }
    else {
      _h_proton_p->fill(modp);
      _h_proton_x->fill(map2string(xp, 1));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_kaon_p, 1. / sumOfWeights());
  scale(_h_kaon_x, 1. / sumOfWeights());
  for (auto& b : _h_kaon_x->bins()) {
    size_t idx = b.index();
    if (idx >= 9) idx += 1;
    b.scaleW(1. / _axis[0].width(idx));
  }
  scale(_h_proton_p, 1. / sumOfWeights());
  scale(_h_proton_x, 1. / sumOfWeights());
  for (auto& b : _h_proton_x->bins()) {
    const size_t idx = b.index();
    b.scaleW(1. / _axis[1].width(idx));
  }
}

/// @}

string map2string(const double value, const size_t type) const {
  const size_t idx = _axis[type].index(value);
  if (idx && idx < 9) return _edges[type][idx - 1];
  if (idx > 9 && idx <= _edges[type].size() + 1) return _edges[type][idx - 2];
  return "OTHER";
}


/// @name Histograms
/// @{
Histo1DPtr _h_kaon_p, _h_proton_p;
BinnedHistoPtr<string> _h_kaon_x, _h_proton_x;
vector<string> _edges[2];
YODA::Axis<double> _axis[2];
/// @}

};

RIVET_DECLARE_PLUGIN(DELPHI_1995_I394052);

} ```