Rivet analyses

title: ZEUS_1999_I500267

Measurement of High-$Q^2$ Neutral-Current $e^+p$ Deep Inelastic Scattering Cross-Sections at HERA

Experiment: ZEUS (HERA Run I)

Inspire ID: 500267

Status: VALIDATED

Authors: - Andrii Verbytskyi

References: - Eur.Phys.J.C 11 (1999) 427-445 - arXiv: hep-ex/9905032

Beams: p+ e+

Beam energies: (820.0, 27.5)GeV

Run details: - Inclusive high $Q^2$ DIS

The $e^+p$ neutral-current deep inelastic scattering differential cross-sections $d\sigma/dQ^2$, for $Q^2$ > 400 $GeV^2$, $d\sigma/dx$ and $d\sigma/dy$, for $Q^2$ > 400, 2500 and 10000 $GeV^2$, have been measured with the ZEUS detector at HERA. The data sample of $47.7 pb^{-1}$ was collected at a center-of-mass energy of 300 GeV. The cross-section, $d\sigma/dQ^2$, falls by six orders of magnitude between $Q^2 = 400$ and $40000 GeV^2$. The predictions of the Standard Model are in very good agreement with the data. Complementing the observations of time-like $Z^0$ contributions to fermion-antifermion annihilation, the data provide direct evidence for the presence of $Z^0$ exchange in the space-like region explored by deep inelastic scattering.

Source code:ZEUS_1999_I500267.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DISKinematics.hh"

namespace Rivet {

/// @brief Measurement of High-$Q^2$ Neutral-Current in DIS class ZEUS_1999_I500267 : public Analysis {

public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ZEUS_1999_I500267);

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

/// Book histograms and initialise projections before the run
void init() {

  const DISKinematics& diskin = DISKinematics();
  declare(diskin, "Kinematics");

  book(_h_Q2, 1, 1, 1);
  book(_h_x[0], 2, 1, 1);
  book(_h_x[1], 3, 1, 1);
  book(_h_x[2], 4, 1, 1);
}

/// Perform the per-event analysis
void analyze(const Event& event) {

  /// DIS kinematics
  const DISKinematics& dk = apply<DISKinematics>(event, "Kinematics");

  double q2 = dk.Q2();
  double x = dk.x();
  double y = dk.y();

  if (y > 0.95) vetoEvent;
  if (q2 < 400) vetoEvent;
  if (q2 > 400) _h_x[0]->fill(x);
  if (q2 > 2500) _h_x[1]->fill(x);
  if (q2 > 10000) _h_x[2]->fill(x);
  _h_Q2->fill(q2);
}

/// Normalise histograms etc., after the run
void finalize() {
  const double norm = crossSection() / picobarn / sumOfWeights();
  scale(_h_Q2, norm);
  scale(_h_x[0], norm);
  scale(_h_x[1], norm);
  scale(_h_x[2], norm);
}

private:

Histo1DPtr _h_Q2;
Histo1DPtr _h_x[3];

};

RIVET_DECLARE_PLUGIN(ZEUS_1999_I500267);

} ```