Rivet analyses

title: JADE_1986_I231554

$\gamma\gamma\to p \bar{p}$ for centre-of-mass energies between 2 and 2.6 GeV

Experiment: JADE (PETRA)

Inspire ID: 231554

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett.B 130 (1983) 449-453

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma to hadrons

Measurement of the differential cross section for $\gamma\gamma\to p \bar{p}$ for $2 \text{GeV} < W < 2.6 \text{GeV}$. Both the cross section as a function of the centre-of-mass energy of the photonic collision, and the differential cross section with respect to the proton scattering angle are measured.

Source code:JADE_1986_I231554.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief gamma gamma -> p pbar class JADE_1986_I231554 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(JADE_1986_I231554);


/// @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, 2., 2.6)) {
    book(_cProton, "TMP/proton", refData(1, 1, 1));
    book(_h_cTheta, 2, 1, 1);
  }
  else {
    throw Error("Invalid CMS energy for JADE_1986_I231554");
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  Particles part = apply<FinalState>(event, "FS").particles();
  if (part.size() != 2) vetoEvent;
  double cTheta(0.);
  bool foundP(false), foundM(false);
  for (const Particle& p : part) {
    if (p.pid() == PID::PROTON) {
      foundP = true;
      cTheta = abs(p.momentum().z() / p.momentum().p3().mod());
    }
    else if (p.pid() == PID::ANTIPROTON)
      foundM = true;
  }
  if (!foundP || !foundM) vetoEvent;
  if (cTheta <= 0.6) _cProton->fill(sqrtS() / GeV);
  if (_h_cTheta) _h_cTheta->fill(cTheta);
}


/// Normalise histograms etc., after the run
void finalize() {
  const double fact = crossSection() / nanobarn / sumOfWeights();
  if (_h_cTheta) scale(_h_cTheta, fact);
  scale(_cProton, fact);
  Estimate1DPtr tmp;
  book(tmp, 1, 1, 1);
  barchart(_cProton, tmp);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_cTheta, _cProton;
/// @}

};

RIVET_DECLARE_PLUGIN(JADE_1986_I231554);

} ```