Rivet analyses

title: TASSO_1986_I230950

$\pi^0$ spectrum in $e^+e^-$ at 34.4 GeV

Experiment: TASSO (Petra)

Inspire ID: 230950

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C33 (1986) 13, 1986

Beams: e+ e-

Beam energies: (17.2, 17.2)GeV

Run details: - e+ e- to hadrons

Measurement of the $\pi^0$ spectrum in $e^+e^-$ collisions for a centre-of-mass energy of 34.4 GeV by the TASSO experiment at Petra.

Source code:TASSO_1986_I230950.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Add a short analysis description here class TASSO_1986_I230950 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1986_I230950);


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

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

  // Initialise and register projections
  declare(Beam(), "Beams");
  declare(UnstableParticles(), "UFS");

  // Book histograms
  book(_h_p, 1, 1, 1);
  book(_h_x, 2, 1, 1);
}


/// 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);

  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid == PID::PI0)) {
    double modp = p.p3().mod();
    double xE = p.E() / meanBeamMom;
    double beta = modp / p.E();
    _h_p->fill(modp);
    _h_x->fill(xE, 1. / beta);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_p, crossSection() / nanobarn / sumOfWeights());
  scale(_h_x, sqr(sqrtS()) * crossSection() / microbarn / sumOfWeights());
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_p, _h_x;
/// @}

};

RIVET_DECLARE_PLUGIN(TASSO_1986_I230950);

} ```