Rivet analyses
title: ZEUS_2007_I753991
High E_T Dijet Photoproduction events at HERA
Experiment: ZEUS (HERA)
Inspire ID: 753991
Status: VALIDATED
Authors: - Bradley Pattengale - Matthew Wing
References: - Phys.Rev.D 76 (2007) 072011 - DOI:10.1103/PhysRevD.76.072011 - arXiv: 0706.3809
Beams: p+ e+, p+ e-
Beam energies: (920.0, 27.5); (920.0, 27.5)GeV
Run details: - Dijet photoproduction in ep collisions. Minimum jet pT = 15 GeV
Cross sections of dijets from photoproduction are shown from collisons between protons and electrons/positrons with beam energies 920GeV and 27.5GeV, respectively. Jet with high transverse energies $E_t^{jet1} > 20GeV,\ E_t^{jet2}>15GeV$ were selected. This data is compared to next-to leading order QCD calculations, and measurements were found that show sensitivity to parton distribution functions of both the proton and photon, and to beyond next-to leading order QCD calculations.
Source code:ZEUS_2007_I753991.cc
```c++ // -- C++ --
include "Rivet/Analysis.hh"
include "Rivet/Projections/Beam.hh"
include "Rivet/Projections/DISKinematics.hh"
include "Rivet/Projections/FastJets.hh"
namespace Rivet {
/// @brief 2007 Dijet Photoproduction Paper of HERA e-P and e+P collisions from 1998-2000 class ZEUS_2007_I753991 : public Analysis { public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ZEUS_2007_I753991);
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
FinalState fs;
declare(FastJets(fs, fastjet::JetAlgorithm::kt_algorithm, fastjet::RecombinationScheme::Et_scheme, 1.0),
"Jets");
declare(DISKinematics(), "Kinematics");
// Histograms
book(_h_etbar[1], 1, 1, 1); // Table 2
book(_h_etbar[0], 2, 1, 1); // Table 3
book(_h_etjet1[1], 3, 1, 1); // Table 4
book(_h_etjet1[0], 4, 1, 1); // Table 5
book(_h_etabar[1], 5, 1, 1); // Table 6
book(_h_etabar[0], 6, 1, 1); // Table 7
book(_h_xpobs[1], 7, 1, 1); // Table 8
book(_h_xpobs[0], 8, 1, 1); // Table 9
book(_h_deltaphi[1], 9, 1, 1); // Table 10
book(_h_deltaphi[0], 10, 1, 1); // Table 11
book(_h_xpobs2, 11, 1, 1); // Table 12
book(_h_xpobs3, 12, 1, 1); // Table 13
book(_h_xpobs4, 13, 1, 1); // Table 14
book(_h_xpobs5, 14, 1, 1); // Table 15
book(_h_xpobs6, 15, 1, 1); // Table 16
book(_h_xpobs7, 16, 1, 1); // Table 17
book(_h_xpobs8, 17, 1, 1); // Table 18
book(_h_xpobs9, 18, 1, 1); // Table 19
book(_h_xyobs, 19, 1, 1); // Table 20
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Determine kinematics
const DISKinematics& kin = apply<DISKinematics>(event, "Kinematics");
if (kin.failed()) vetoEvent;
const int orientation = kin.orientation();
// Q2 cut and inelasticity cut
if (kin.Q2() > 1 * GeV2) vetoEvent;
if (!inRange(kin.y(), 0.2, 0.85)) vetoEvent;
// Jet Selection
const Jets jets = apply<FastJets>(event, "Jets")
.jets(Cuts::Et > 15 * GeV && Cuts::etaIn(-1 * orientation, 3 * orientation),
cmpMomByEt);
MSG_DEBUG("Jet Multiplicity = " << jets.size());
if (jets.size() < 2) vetoEvent;
const Jet& j1 = jets[0];
const Jet& j2 = jets[1];
if (j1.Et() < 20 * GeV) vetoEvent;
const double eta1 = orientation * j1.eta();
const double eta2 = orientation * j2.eta();
if ((eta1 > 2.5) && (eta2 > 2.5)) vetoEvent;
// Jet eta bar and E bar calculation
const double etabar = (eta1 + eta2) / 2;
const double ebar = (j1.Et() + j2.Et()) / 2;
// Calculate x_y^obs and x_p^obs
const double xyobs = (j1.Et() * exp(-eta1) + j2.Et() * exp(-eta2))
/ (2 * kin.y() * kin.beamLepton().E());
const size_t i_xyobs = (xyobs < 0.75) ? 0 : 1;
const double xpobs = (j1.Et() * exp(eta1) + j2.Et() * exp(eta2)) / (2 * kin.beamHadron().E());
// Delta Phi Calculation
const double phi1 = j1.phi();
const double phi2 = j2.phi();
const double dPhi = mapAngleMPiToPi(phi1 - phi2);
const double deltaPhi = abs(dPhi);
// Fill Histograms
_h_etbar[i_xyobs]->fill(ebar / GeV);
_h_etjet1[i_xyobs]->fill(j1.Et() / GeV);
_h_etabar[i_xyobs]->fill(etabar);
_h_xpobs[i_xyobs]->fill(xpobs);
_h_deltaphi[i_xyobs]->fill(deltaPhi);
// Symmetrize histograms with different eta regions
for (size_t isel = 0; isel < 2; ++isel) {
double etaJet1 = (isel == 0) ? orientation * j1.eta() : orientation * j2.eta();
double etaJet2 = (isel == 0) ? orientation * j2.eta() : orientation * j1.eta();
if (i_xyobs > 0.75) {
if (inRange(etaJet1, 0, 1) && inRange(etaJet2, 2, 3)) {
if (j1.Et() > 25 * GeV) {
_h_xpobs2->fill(xpobs);
}
if (j1.Et() > 20 * GeV) {
_h_xpobs3->fill(xpobs);
}
}
else if (inRange(etaJet1, -1, 0) && inRange(etaJet2, 0, 1)) {
if (j1.Et() > 20 * GeV) {
_h_xpobs5->fill(xpobs);
}
}
}
else {
if (inRange(etaJet1, 2, 2.5) && inRange(etaJet2, 2, 3)) {
if (j1.Et() > 20 * GeV) {
_h_xpobs6->fill(xpobs);
}
}
else if (inRange(etaJet1, 1, 2) && inRange(etaJet2, 2, 3)) {
if (j1.Et() > 20 * GeV) {
_h_xpobs8->fill(xpobs);
}
if (j1.Et() > 25 * GeV) {
_h_xpobs9->fill(xpobs);
}
}
}
}
if (i_xyobs > 0.75) {
if (inRange(eta1, 1, 2) && inRange(eta2, 1, 2)) {
if (j1.Et() > 30 * GeV) {
_h_xpobs4->fill(xpobs);
}
}
}
else {
if (inRange(eta1, 1, 2) && inRange(eta2, 1, 2)) {
if (j1.Et() > 25 * GeV) {
_h_xpobs7->fill(xpobs);
}
}
}
_h_xyobs->fill(xyobs);
}
/// Normalise histograms etc., after the run
void finalize() {
const double sf = crossSection() / picobarn / sumOfWeights();
scale(_h_etbar, sf);
scale(_h_etjet1, sf);
scale(_h_etabar, sf);
scale(_h_xpobs, sf);
scale(_h_deltaphi, sf);
scale(_h_xpobs2, sf);
scale(_h_xpobs3, sf);
scale(_h_xpobs4, sf);
scale(_h_xpobs5, sf);
scale(_h_xpobs6, sf);
scale(_h_xpobs7, sf);
scale(_h_xpobs8, sf);
scale(_h_xpobs9, sf);
scale(_h_xyobs, sf);
}
/// @}
private:
/// @name Histograms
/// @{
Histo1DPtr _h_etbar[2], _h_etjet1[2], _h_etabar[2], _h_xpobs[2], _h_deltaphi[2];
Histo1DPtr _h_xpobs2, _h_xpobs3, _h_xpobs4, _h_xpobs5, _h_xpobs6;
Histo1DPtr _h_xpobs7, _h_xpobs8, _h_xpobs9, _h_xyobs;
/// @}
};
RIVET_DECLARE_PLUGIN(ZEUS_2007_I753991);
} ```