Rivet analyses

γγ → π⁺π⁻/K⁺K⁻ for centre-of-mass energies between 1.7 and 3.5 GeV

Experiment: MARKII (PEP)

Inspire ID: 220003

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 56 (1986) 207

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma to hadrons

Measurement of the differential cross section for γγ → π⁺π⁻/K⁺K⁻ for 1.7GeV < W < 3.5GeV.

Source code:`MARKII_1986_I220003.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {


  /// @brief gamma gamma -> pi+pi-/K+ K-
  class MARKII_1986_I220003 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1986_I220003);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      // check CMS energy in range
      if (sqrtS() < 1.5 * GeV || sqrtS() > 5 * GeV) throw Error("Invalid CMS energy for MARKII_1986_I220003");
      book(_cPiK[0], "/TMP/nPiK_0");
      book(_cPiK[1], "/TMP/nPiK_1");
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      Particles part = apply<FinalState>(event, "FS").particles();
      if (part.size() != 2) vetoEvent;
      if (part[0].pid() != -part[1].pid()) vetoEvent;
      double cTheta(0.);
      bool foundPi(false), foundK(false);
      for (const Particle& p : part) {
        if (p.pid() == PID::PIPLUS) {
          foundPi = true;
          cTheta = abs(p.momentum().z() / p.momentum().p3().mod());
        }
        else if (p.pid() == PID::KPLUS) {
          foundK = true;
          cTheta = abs(p.momentum().z() / p.momentum().p3().mod());
        }
      }
      if (!foundPi && !foundK) vetoEvent;
      if (cTheta > 0.5) vetoEvent;
      if (cTheta > 0.3)
        _cPiK[1]->fill();
      else
        _cPiK[0]->fill();
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection() / nanobarn / sumOfWeights();
      for (unsigned int ix = 0; ix < 2; ++ix) {
        double sigma = _cPiK[ix]->val() * fact;
        double error = _cPiK[ix]->err() * fact;
        Estimate1DPtr cross;
        book(cross, 1, 1, 1 + ix);
        for (auto& b : cross->bins()) {
          if (inRange(sqrtS(), b.xMin(), b.xMax())) {
            b.set(sigma, error);
          }
        }
      }
    }

    ///@}


    /// @name Histograms
    ///@{
    CounterPtr _cPiK[2];
    ///@}
  };


  RIVET_DECLARE_PLUGIN(MARKII_1986_I220003);

}

Rivet analyses

γγ → π+π−/K+K− for centre-of-mass energies between 1.7 and 3.5 GeV

Source code:MARKII_1986_I220003.cc

γγ → π⁺π⁻/K⁺K⁻ for centre-of-mass energies between 1.7 and 3.5 GeV

Source code:`MARKII_1986_I220003.cc`