Rivet analyses

title: LHCF_2018_I1518782

Measurement of forward photon production cross-section in proton-proton collisions at $\mathrm{\sqrt{s}=13\,TeV}$ with the LHCf detector

Experiment: LHCF (LHC)

Inspire ID: 1518782

Status: VALIDATED

Authors: - Eugenio Berti - LHCf collaboration

References: - Phys.Lett. B780 (2018) 233-239 - DOI: 10.1016/j.physletb.2017.12.050 - arXiv: 1703.07678

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - Inclusive differential production cross section of forward photons produced in p-p collisions at $\mathrm{\sqrt{s}=13\,TeV}$. Cross section is expressed as a function of energy in two different pseudorapidity regions, namely $\eta>10.94$ and $8.81<\eta<8.99$. The measurements refer to all photons directly produced in the collisions or resulting from the decay of short life particles ($\mathrm{c \tau<1\,cm}$).

In this paper, we report the production cross-section of forward photons in the pseudorapidity regions of $\eta>10.94$ and $8.99>\eta>8.81$, measured by the LHCf experiment with proton-proton collisions at $\mathrm{\sqrt{s}=13\,TeV}$. The results from the analysis of $\mathrm{0.191\,nb^{-1}}$ of data obtained in June 2015 are compared to the predictions of several hadronic interaction models that are used in air-shower simulations for ultra-high-energy cosmic rays. Although none of the models agree perfectly with the data, EPOS-LHC shows the best agreement with the experimental data among the models.

Source code:LHCF_2018_I1518782.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Forward photon production cross-section at 13 TeV class LHCF_2018_I1518782 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(LHCF_2018_I1518782);

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

void init() {
  declare(FinalState(), "FS");
  book(_h_n_en_eta1, 1, 1, 1);
  book(_h_n_en_eta2, 2, 1, 1);
}

void analyze(const Event& event) {

  // Select photons above threshold
  Particles fs_particles = apply<FinalState>(event, "FS")
                               .particles(Cuts::abspid == PID::PHOTON && Cuts::E >= 200 / GeV
                                          && Cuts::abseta > 8.81);

  for (const Particle& p : fs_particles) {
    // Double analysis efficiency with a two-sided LHCf --- NOTE: taken care of in finalize division by 2
    const double eta = abs(p.eta());
    const double energy = p.E() / GeV;
    if (eta > 10.94) _h_n_en_eta1->fill(energy);
    if (eta < 8.99) _h_n_en_eta2->fill(energy);
  }
}

void finalize() {
  // Norm to cross-section
  scale(_h_n_en_eta1, crossSection() / millibarn / sumOfWeights() / 2.);
  scale(_h_n_en_eta2, crossSection() / millibarn / sumOfWeights() / 2.);
}
/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_n_en_eta1, _h_n_en_eta2;
/// @}

};

RIVET_DECLARE_PLUGIN(LHCF_2018_I1518782); } ```