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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: 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
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/DISKinematics.hh"
 4
 5
 6namespace Rivet {
 7
 8/// @brief  Measurement of High-$Q^2$ Neutral-Current in DIS
 9class ZEUS_1999_I500267 : public Analysis {
10
11  public:
12      /// Constructor
13      RIVET_DEFAULT_ANALYSIS_CTOR(ZEUS_1999_I500267);
14
15      /// @name Analysis methods
16      /// @{
17
18      /// Book histograms and initialise projections before the run
19      void init() {
20
21          const DISKinematics& diskin = DISKinematics();
22          declare(diskin,"Kinematics");
23
24          book(_h_Q2,   1, 1, 1);
25          book(_h_x[0], 2, 1, 1);
26          book(_h_x[1], 3, 1, 1);
27          book(_h_x[2], 4, 1, 1);
28
29      }
30
31      /// Perform the per-event analysis
32      void analyze(const Event& event) {
33
34          /// DIS kinematics
35          const DISKinematics& dk = apply<DISKinematics>(event, "Kinematics");
36
37          double q2  = dk.Q2();
38          double x   = dk.x();
39          double y   = dk.y();
40
41          if (y > 0.95) vetoEvent;
42          if (q2 < 400) vetoEvent;
43          if (q2 > 400) _h_x[0]->fill(x);
44          if (q2 > 2500) _h_x[1]->fill(x);
45          if (q2 > 10000) _h_x[2]->fill(x);
46          _h_Q2->fill(q2);
47
48      }
49
50      /// Normalise histograms etc., after the run
51      void finalize() {
52          const double norm = crossSection()/picobarn/sumOfWeights();
53          scale(_h_Q2, norm);
54          scale(_h_x[0],norm);
55          scale(_h_x[1], norm);
56          scale(_h_x[2], norm);
57      }
58
59    private:
60
61      Histo1DPtr _h_Q2;
62      Histo1DPtr _h_x[3];
63  };
64
65  RIVET_DECLARE_PLUGIN(ZEUS_1999_I500267);
66
67
68}