Rivet analyses

Measurement of High-Q2 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 Q2 DIS

The e+p neutral-current deep inelastic scattering differential cross-sections dσ/dQ2, for Q2 > 400 GeV2, dσ/dx and dσ/dy, for Q2 > 400, 2500 and 10000 GeV2, have been measured with the ZEUS detector at HERA. The data sample of 47.7pb−1 was collected at a center-of-mass energy of 300 GeV. The cross-section, dσ/dQ2, falls by six orders of magnitude between Q2 = 400 and 40000GeV2. The predictions of the Standard Model are in very good agreement with the data. Complementing the observations of time-like Z0 contributions to fermion-antifermion annihilation, the data provide direct evidence for the presence of Z0 exchange in the space-like region explored by deep inelastic scattering.

Source code:ZEUS_1999_I500267.cc

// -*- 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);


}