Rivet analyses

title: CELLO_1989_I276764

Photon, $\pi^0$ and $\eta$ spectra at 35 GeV

Experiment: CELLO (Petra)

Inspire ID: 276764

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C47 (1990) 1-10, 1990

Beams: e+ e-

Beam energies: (17.5, 17.5)GeV

Run details: - e+ e- to hadrons

Measurement of the $\gamma$, $\pi^0$ and $\eta$ energy fractions in $e^+e^-$ collisions for centre-of-mass energy of 35 GeV by the CELLO experiment at Petra. Only the bin centroids are given in the paper and HEPdata so the bin widths have been inferred.

Source code:CELLO_1989_I276764.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Add a short analysis description here class CELLO_1989_I276764 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CELLO_1989_I276764);


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

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

  // Initialise and register projections
  declare(Beam(), "Beams");
  declare(FinalState(), "FS");
  declare(UnstableParticles(Cuts::pid == 111 || Cuts::pid == 221), "UFS");
  // Book histograms
  for (unsigned int ix = 0; ix < 4; ++ix) book(_h[ix], 2 + ix, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  if (_edges[0].empty()) {
    for (unsigned int ix = 0; ix < 4; ++ix) _edges[ix] = _h[ix]->xEdges();
  }
  // at least 5 charged FS particles
  const FinalState& fs = apply<FinalState>(event, "FS");
  const size_t numParticles = fs.particles().size();

  if (numParticles < 5) {
    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);

  // Final state to get particle spectra
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    double xE = p.E() / meanBeamMom;
    if (p.pid() == 111) {
      _h[1]->fill(map2string(xE, 1));
      _h[2]->fill(map2string(xE, 2));
    }
    else
      _h[3]->fill(map2string(xE, 3));
  }
  for (const Particle& p : apply<FinalState>(event, "FS").particles(Cuts::pid == 22)) {
    _h[0]->fill(map2string(p.E() / meanBeamMom, 0));
  }
}

string map2string(const double val, const size_t axis) const {
  const size_t idx = _axes[axis].index(val);
  if (idx && idx <= _edges[axis].size()) return _edges[axis][idx - 1];
  return "OTHER";
}

/// Normalise histograms etc., after the run
void finalize() {
  double fact = sqr(sqrtS()) / GeV2 * crossSection() / microbarn / sumOfWeights();
  for (unsigned int ix = 0; ix < 4; ++ix) {
    scale(_h[ix], fact);
    for (auto& b : _h[ix]->bins()) {
      const size_t idx = b.index();
      b.scaleW(1. / _axes[ix].width(idx));
    }
  }
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _h[4];
vector<string> _edges[4];
YODA::Axis<double> _axes[4] = {
    YODA::Axis<double>({0.01,   0.02,  0.03,  0.04,  0.05,   0.06,  0.07,  0.08,   0.09,  0.10,
                        0.11,   0.12,  0.13,  0.14,  0.15,   0.16,  0.175, 0.195,  0.215, 0.235,
                        0.255,  0.275, 0.295, 0.315, 0.3535, 0.394, 0.434, 0.4735, 0.514, 0.555,
                        0.5965, 0.641, 0.691, 0.74,  0.785,  0.839, 0.901}),
    YODA::Axis<double>({0.039, 0.059, 0.079, 0.109, 0.139, 0.193, 0.277, 0.439}),
    YODA::Axis<double>({0.2705, 0.3415, 0.412, 0.482, 0.552, 0.6225, 0.6935, 0.7805, 0.876, 0.962}),
    YODA::Axis<double>({0.0225, 0.0775, 0.1325, 0.2875, 0.4625, 0.9175})};
/// @}

};

RIVET_DECLARE_PLUGIN(CELLO_1989_I276764);

} ```