Rivet analyses

title: TASSO_1982_I168232

$\pi^0$ spectrum in $e^+e^-$ at 14 and 34 GeV

Experiment: TASSO (TASSO)

Inspire ID: 168232

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B108 (1982) 71-76, 1982

Beams: e+ e-

Beam energies: (7.0, 7.0); (17.0, 17.0)GeV

Run details: - e+ e- to hadrons.

Measurement of the $\pi^0$ spectrum in $e^+e^-$ collisions for centre-of-mass energies of 14 and 34 GeV by the TASSO experiment at Petra.

Source code:TASSO_1982_I168232.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief pi0 spectrum at 14 and 34 GeV class TASSO_1982_I168232 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1982_I168232);


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

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


  declare(Beam(), "Beams");
  declare(UnstableParticles(), "UFS");

  // Book histograms
  size_t ih = 2;
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;
    book(_h[en + "E"], ih, 1, 1);
    book(_h[en + "p"], ih, 2, 2);
    book(_h[en + "x"], ih, 3, 3);
    ++ih;
  }
  raiseBeamErrorIf(_sqs.empty());
}


/// 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 = 0.5 * (beams.first.p3().mod() + beams.second.p3().mod());
  MSG_DEBUG("Avg beam momentum = " << meanBeamMom);

  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid == PID::PI0)) {
    if (!p.parents().empty() && p.parents()[0].pid() == PID::K0S) continue;
    double xE = p.E() / meanBeamMom;
    double beta = p.p3().mod() / p.E();
    _h[_sqs + "E"]->fill(p.E() / GeV);
    _h[_sqs + "p"]->fill(p.p3().mod() / GeV);
    _h[_sqs + "x"]->fill(xE, 1.0 / beta);
  }
}


/// Normalise histograms etc., after the run
void finalize() {

  for (auto& item : _h) {
    if (item.first.find("x") != string::npos) {
      const double en = stod(item.first.substr(0, 2));
      scale(item.second, sqr(en) * crossSection() / microbarn / sumOfWeights());
    }
    else {
      scale(item.second, crossSection() / nanobarn / sumOfWeights());
    }
  }
}

/// @}


/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(TASSO_1982_I168232); } ```