Rivet analyses

title: BELLE_2003_I629334

$\gamma\gamma\to K^+K^-$ for centre-of-mass energies between 1.4 and 2.4 GeV

Experiment: BELLE (KEKB)

Inspire ID: 629334

Status: VALIDATED

Authors: - Peter Richardson

References: - Eur.Phys.J.C 32 (2003) 323-336, 2003

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma to hadrons

Measurement of the differential cross section for $\gamma\gamma\to K^+K^-$ for $1.4 \text{GeV} < W < 2.4 \text{GeV}$. 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 kaon scattering angle are measured.

Source code:BELLE_2003_I629334.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief gamma gamma -> K+K- class BELLE_2003_I629334 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2003_I629334);


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

/// Book histograms and initialise projections before the run
void init() {
  // Final state
  declare(FinalState(), "FS");
  // check CMS energy in range
  if (sqrtS() < 1.4 * GeV || sqrtS() > 2.4 * GeV)
    throw Error("Invalid CMS energy for BELLE_2003_I629334");
  // bin for the angle plots
  int ibin = (sqrtS() - 1.40) / 0.04;
  book(_h_cTheta, 2 + ibin / 4, 1, ibin % 4 + 1);
  book(_cK, "/TMP/nK");
}


/// 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::KPLUS) {
      foundP = true;
      cTheta = abs(p.momentum().z() / p.momentum().p3().mod());
    }
    else if (p.pid() == PID::KMINUS)
      foundM = true;
  }
  if (!foundP || !foundM) vetoEvent;
  if (cTheta <= 0.6) _cK->fill();
  if (_h_cTheta) _h_cTheta->fill(cTheta);
}


/// Normalise histograms etc., after the run
void finalize() {
  double fact = crossSection() / nanobarn / sumOfWeights();
  if (_h_cTheta) scale(_h_cTheta, fact);
  double sigma = _cK->val() * fact;
  double error = _cK->err() * fact;
  Estimate1DPtr mult;
  book(mult, 1, 1, 1);
  for (auto& b : mult->bins()) {
    if (inRange(sqrtS(), b.xMin(), b.xMax())) {
      b.set(sigma, error);
    }
  }
}

///@}


/// @name Histograms
///@{
Histo1DPtr _h_cTheta;
CounterPtr _cK;
///@}

};

RIVET_DECLARE_PLUGIN(BELLE_2003_I629334);

} ```