Rivet analyses

γγ → pp̄ 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 γγ → pp̄ for 2GeV < W < 2.6GeV. 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++ -*-
#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);

}