Rivet analyses

title: TASSO_1986_I228876

$\gamma\gamma\to\pi^+\pi^-\pi^0$ between 0.9 and 2.4 GeV

Experiment: TASSO (DORIS)

Inspire ID: 228876

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys.C 31 (1986) 537

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma to hadrons, K0S and pi0 mesons must be set stable

Measurement of the differential cross section for $\gamma\gamma\to\pi^+\pi^-\pi^0$for $0.9 \text{GeV} < W < 2.4 \text{GeV}$. The cross section is measured as a function of the centre-of-mass energy of the photonic collision for the final state only

Source code:TASSO_1986_I228876.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief gamma gamma -> pi+pi-pi0 class TASSO_1986_I228876 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1986_I228876);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  // book histos
  if (inRange(sqrtS() / GeV, 0.9, 2.4)) {
    book(_nMeson, "TMP/nMeson", refData(1, 1, 1));
  }
  else {
    throw Error("Invalid CMS energy for TASSO_1986_I228876");
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  // find the final-state particles
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  // check the 3 meson final state
  if (ntotal == 3 && nCount[PID::PI0] == 1 && nCount[PID::PIPLUS] == 1 && nCount[PID::PIMINUS] == 1) {
    _nMeson->fill(sqrtS() / GeV);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_nMeson, crossSection() / nanobarn / sumOfWeights());
  Estimate1DPtr tmp;
  book(tmp, 1, 1, 1);
  barchart(_nMeson, tmp);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _nMeson;
/// @}

};

RIVET_DECLARE_PLUGIN(TASSO_1986_I228876);

} ```