Rivet analyses

title: H1_1998_I477556

Charged-particle photoproduction analysis

Experiment: H1 (HERA Run I)

Inspire ID: 477556

Status: UNVALIDATED

Authors: - Ilkka Helenius

References: - Eur.Phys.J.C10:363,1999 - DESY 98/148 - arXiv: hep-ex/9810020

Beams: p+ 22

Beam energies: (820.0, 12.2)GeV

Run details: - 820 GeV protons colliding with 27.5 GeV positrons; Direct and resolved photoproduction of charged particles; particle pseudorapidity $|\eta| < 1$

H1 photoproduction of charged particles from proton--positron collisions at beam energies of 820~GeV on 27.5~GeV. Notice that the flux factor has been divided out and this is for p+gamma at the average energy for proton-photon system.

Source code:H1_1998_I477556.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief H1 charged particle photoproduction class H1_1998_I477556 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(H1_1998_I477556);

/// @name Analysis methods
//@{

// Book projections and histograms
void init() {

  // Acceptance
  const FinalState fs(Cuts::abseta < 1 && Cuts::pT > 2 * GeV);
  const ChargedFinalState cfs(fs);
  declare(cfs, "CFS");

  // Table 1, pT spectra
  book(_h_ch_pT, 1, 1, 1);
  // Table 2, eta distributions with different pT cuts.
  book(_h_ch_eta[0], 2, 1, 1);
  book(_h_ch_eta[1], 2, 1, 2);
}

// Do the analysis
void analyze(const Event& event) {

  // Loop over charged particles and fill histograms.
  const Particles& particles = apply<FinalState>(event, "CFS").particles();
  for (const Particle& p : particles) {

    // Cross section for dsigma/dpt^2deta but as a function of pT.
    // Use the conversion factor as a weight.
    _h_ch_pT->fill(p.pt() / GeV, 1.0 / (2 * p.pt() / GeV));
    _h_ch_eta[0]->fill(p.eta());
    if (p.pt() > 3. * GeV) _h_ch_eta[1]->fill(p.eta());
  }
}

// Finalize
void finalize() {
  const double sf = crossSection() / nanobarn / sumOfWeights();
  // For d^2sigma/dpT^2deta scale with eta bin width.
  scale(_h_ch_pT, 0.5 * sf);
  scale(_h_ch_eta, sf);
}

//@}

private:

/// @name Histograms
//@{
Histo1DPtr _h_ch_pT, _h_ch_eta[2];
//@}

};

RIVET_DECLARE_PLUGIN(H1_1998_I477556);

} ```