Rivet analyses
title: ZEUS_2007_I756660
Three- and four-jet final states in photoproduction at HERA
Experiment: ZEUS (HERA)
Inspire ID: 756660
Status: VALIDATED
Authors: - Vithyaban Anjelo Narendran - Bradley Pattengale - Matthew Wing
References: - Nucl.Phys.B 792 (2008) 1-47 - DOI:10.1016/j.nuclphysb.2007.08.021 - arXiv: 0707.3749
Beams: p+ e+, p+ e-, p+ e+, p+ e-
Beam energies: (920.0, 27.5); (920.0, 27.5); (820.0, 27.5); (820.0, 27.5)GeV
Run details: - Photoproduction in ep collisions, jets with pT>6 GeV
Three- and four-jet events were measured from photoproduction events at HERA. This data was taken with center of mass energies of $\sqrt{s} = 300$ GeV and $\sqrt{s} = 318$ GeV. The kinematic cuts applied were $E_T^{jet} > 6$ GeV, $|\eta| < 2.4$, $Q^2 < 1$ GeV$^2$, and $0.2 \leq y \leq 0.85$. Cross sections are presented as a function of $M_{nj}$, $x_{\gamma}$, $E_T^{jet}$, $\eta$, $y$, and $cos(\phi_3)$
Source code:ZEUS_2007_I756660.cc
```c++ // -- C++ --
include "Rivet/Analysis.hh"
include "Rivet/Projections/Beam.hh"
include "Rivet/Projections/DISKinematics.hh"
include "Rivet/Projections/DirectFinalState.hh"
include "Rivet/Projections/FastJets.hh"
include "Rivet/Projections/FinalState.hh"
namespace Rivet {
/// @brief Three- and four-jet final states in photoproduction at HERA class ZEUS_2007_I756660 : public Analysis { public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ZEUS_2007_I756660);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Jets
const FinalState fs;
declare(FastJets(fs, fastjet::JetAlgorithm::kt_algorithm, fastjet::RecombinationScheme::pt2_scheme,
1.0),
"Jets");
// DIS Kinematics
declare(DISKinematics(), "Kinematics");
// Book Histos
book(_h["M3j"], 1, 1, 1); // T2, F3A
book(_h["M4j"], 2, 1, 1); // T3, F3B
// T4, F4A,4B
book(_h["x_gamma_obs_low_M3j"], 3, 1, 1);
book(_h["x_gamma_obs_high_M3j"], 3, 1, 2);
// T5, F4C,4D
book(_h["x_gamma_obs_low_M4j"], 4, 1, 1);
book(_h["x_gamma_obs_high_M4j"], 4, 1, 2);
// T6, F5A,5B
book(_h["y_low_M3j"], 5, 1, 1);
book(_h["y_high_M3j"], 5, 1, 2);
// T7, F5C,5D
book(_h["y_low_M4j"], 6, 1, 1);
book(_h["y_high_M4j"], 6, 1, 2);
// T8, F6A,6B
book(_h["Et1_low_M3j"], 7, 1, 1);
book(_h["Et1_high_M3j"], 7, 1, 2);
// T9, F6A,6B
book(_h["Et2_low_M3j"], 8, 1, 1);
book(_h["Et2_high_M3j"], 8, 1, 2);
// T10, F6A,6B
book(_h["Et3_low_M3j"], 9, 1, 1);
book(_h["Et3_high_M3j"], 9, 1, 2);
// T11, F7A,7B
book(_h["Et1_low_M4j"], 10, 1, 1);
book(_h["Et1_high_M4j"], 10, 1, 2);
// T12, F7A,7B
book(_h["Et2_low_M4j"], 11, 1, 1);
book(_h["Et2_high_M4j"], 11, 1, 2);
// T13, F7A,7B
book(_h["Et3_low_M4j"], 12, 1, 1);
book(_h["Et3_high_M4j"], 12, 1, 2);
// T14, F7A,7B
book(_h["Et4_low_M4j"], 13, 1, 1);
book(_h["Et4_high_M4j"], 13, 1, 2);
// T15, F8A,8B
book(_h["Eta1_low_M3j"], 14, 1, 1);
book(_h["Eta1_high_M3j"], 14, 1, 2);
// T16, F8A,8B
book(_h["Eta2_low_M3j"], 15, 1, 1);
book(_h["Eta2_high_M3j"], 15, 1, 2);
// T17, F8A,8B
book(_h["Eta3_low_M3j"], 16, 1, 1);
book(_h["Eta3_high_M3j"], 16, 1, 2);
// T18, F9A,9B
book(_h["Eta1_low_M4j"], 17, 1, 1);
book(_h["Eta1_high_M4j"], 17, 1, 2);
// T19, F9A,9B
book(_h["Eta2_low_M4j"], 18, 1, 1);
book(_h["Eta2_high_M4j"], 18, 1, 2);
// T20, F9A,9B
book(_h["Eta3_low_M4j"], 19, 1, 1);
book(_h["Eta3_high_M4j"], 19, 1, 2);
// T21, F9A,9B
book(_h["Eta4_low_M4j"], 20, 1, 1);
book(_h["Eta4_high_M4j"], 20, 1, 2);
// T22, F10A,10B
book(_h["Cos_phi3_low_M3j"], 21, 1, 1);
book(_h["Cos_phi3_high_M3j"], 21, 1, 2);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// DIS Kinematics & Warnings
const DISKinematics& kin = apply<DISKinematics>(event, "Kinematics");
if (kin.failed()) vetoEvent;
const int orientation = kin.orientation();
if (kin.Q2() > 1 * GeV2) vetoEvent;
if (!inRange(kin.y(), 0.2, 0.85)) vetoEvent;
// Jets
const Jets jets = apply<FastJets>(event, "Jets")
.jets(Cuts::Et > 6 * GeV && Cuts::etaIn(-2.4 * orientation, 2.4 * orientation),
cmpMomByEt);
// Veto event by number of jets
if (jets.size() < 3) vetoEvent;
// Define jet numbers
const Jet& j1 = jets[0];
const Jet& j2 = jets[1];
const Jet& j3 = jets[2];
// Define eta (with orientations)
const double eta1 = orientation * j1.eta(), eta2 = orientation * j2.eta(),
eta3 = orientation * j3.eta();
// Get jet momenta
FourMomentum j1_p(j1.momentum());
FourMomentum j2_p(j2.momentum());
FourMomentum j3_p(j3.momentum());
// Three jet events
if (j3.Et() > 6 * GeV) {
// x_obs_gamma
const double x_gamma_3j = (j1.Et() * exp(-eta1) + j2.Et() * exp(-eta2) + j3.Et() * exp(-eta3))
/ (2 * kin.y() * kin.beamLepton().E());
// Invariant Mass
const double M3j = FourMomentum(j1_p + j2_p + j3_p).mass();
// Three Momentum
ThreeMomentum p3 = j1_p.p3();
ThreeMomentum p4 = j2_p.p3();
ThreeMomentum p5 = j3_p.p3();
ThreeMomentum p_beam = kin.beamHadron().p3() - kin.beamLepton().p3();
Vector3 plane1 = cross(p_beam, p3);
Vector3 plane2 = cross(p4, p5);
const double mag_plane1 = abs(sqrt(sqr(plane1[0]) + sqr(plane1[1]) + sqr(plane1[2])));
const double mag_plane2 = abs(sqrt(sqr(plane2[0]) + sqr(plane2[1]) + sqr(plane2[2])));
const double norm_cos_phi3 = mag_plane1 * mag_plane2;
const double cos_phi3 = (dot(plane1, plane2)) / norm_cos_phi3;
_h["M3j"]->fill(M3j / GeV);
if (inRange(M3j, 25 * GeV, 50 * GeV)) {
_h["x_gamma_obs_low_M3j"]->fill(x_gamma_3j);
_h["y_low_M3j"]->fill(kin.y());
_h["Et1_low_M3j"]->fill(j1.Et());
_h["Et2_low_M3j"]->fill(j2.Et());
_h["Et3_low_M3j"]->fill(j3.Et());
_h["Eta1_low_M3j"]->fill(eta1);
_h["Eta2_low_M3j"]->fill(eta2);
_h["Eta3_low_M3j"]->fill(eta3);
_h["Cos_phi3_low_M3j"]->fill(cos_phi3);
}
if (M3j >= 50 * GeV) {
_h["x_gamma_obs_high_M3j"]->fill(x_gamma_3j);
_h["y_high_M3j"]->fill(kin.y());
_h["Et1_high_M3j"]->fill(j1.Et());
_h["Et2_high_M3j"]->fill(j2.Et());
_h["Et3_high_M3j"]->fill(j3.Et());
_h["Eta1_high_M3j"]->fill(eta1);
_h["Eta2_high_M3j"]->fill(eta2);
_h["Eta3_high_M3j"]->fill(eta3);
_h["Cos_phi3_high_M3j"]->fill(cos_phi3);
}
}
// Four jet events
if (jets.size() > 3) {
const Jet& j4 = jets[3];
if (j4.Et() > 6 * GeV) {
// Jet4 info
FourMomentum j4_p(j4.momentum());
const double eta4 = orientation * j4.eta();
if (abs(eta4) > 2.4) vetoEvent;
// x_obs_gamma
const double x_gamma_4j = (j1.Et() * exp(-eta1) + j2.Et() * exp(-eta2) + j3.Et() * exp(-eta3)
+ j4.Et() * exp(-eta4))
/ (2 * kin.y() * kin.beamLepton().E());
// Invariant Mass
double M4j = FourMomentum(j1_p + j2_p + j3_p + j4_p).mass();
_h["M4j"]->fill(M4j / GeV);
if (inRange(M4j, 25 * GeV, 50 * GeV)) {
_h["x_gamma_obs_low_M4j"]->fill(x_gamma_4j);
_h["y_low_M4j"]->fill(kin.y());
_h["Et1_low_M4j"]->fill(j1.Et());
_h["Et2_low_M4j"]->fill(j2.Et());
_h["Et3_low_M4j"]->fill(j3.Et());
_h["Et4_low_M4j"]->fill(j4.Et());
_h["Eta1_low_M4j"]->fill(eta1);
_h["Eta2_low_M4j"]->fill(eta2);
_h["Eta3_low_M4j"]->fill(eta3);
_h["Eta4_low_M4j"]->fill(eta4);
}
if (M4j >= 50 * GeV) {
_h["x_gamma_obs_high_M4j"]->fill(x_gamma_4j);
_h["y_high_M4j"]->fill(kin.y());
_h["Et1_high_M4j"]->fill(j1.Et());
_h["Et2_high_M4j"]->fill(j2.Et());
_h["Et3_high_M4j"]->fill(j3.Et());
_h["Et4_high_M4j"]->fill(j4.Et());
_h["Eta1_high_M4j"]->fill(eta1);
_h["Eta2_high_M4j"]->fill(eta2);
_h["Eta3_high_M4j"]->fill(eta3);
_h["Eta4_high_M4j"]->fill(eta4);
}
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
scale(_h, crossSection() / picobarn / sumW());
}
/// @}
/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
};
RIVET_DECLARE_PLUGIN(ZEUS_2007_I756660);
} ```