Rivet analyses referenceLHCB_2018_I1662483Measurement of the forward top pair production cross-section in the dilepton channelExperiment: LHCB (LHC) Inspire ID: 1662483 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
Measurement of the top pair cross-section in the dilepton channel, where a muon, electron and one $b$-jet are required to be present in the event. A fiducial cross-section is measuremed where the leptons and jets are required to be within the pseudorapidity acceptance of the LHCb acceptance ($2<\eta<4.5$), and to have a transverse momentum greater than 20 GeV. Additionally leptons are required to be separated from each other by a radial distance ($\Delta R$) of 0.1, and from the $b$-jet by a distance of 0.5. Source code: LHCB_2018_I1662483.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/FinalPartons.hh"
5#include "Rivet/Projections/FastJets.hh"
6#include "Rivet/Projections/LeptonFinder.hh"
7#include "Rivet/Projections/MissingMomentum.hh"
8#include "Rivet/Projections/PromptFinalState.hh"
9
10namespace Rivet {
11
12
13 /// @brief Measurement of forward top pair production in the mu e channel at LHCb
14 ///
15 /// Both leptons with pt > 20 GeV and in pseudorapidity range 2.0 - 4.5.
16 /// Leptons are separated from each other by a dR of 0.1.
17 /// Leading jet is required to be a b-jet with pt > 20 GeV and pseudorapidity in range 2.2 - 4.2.
18 /// The jet is separated from both leptons by dR of 0.5.
19 ///
20 class LHCB_2018_I1662483 : public Analysis {
21 public:
22
23 /// Default constructor
24 RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2018_I1662483);
25
26
27 /// @name Analysis methods
28 /// @{
29
30 /// Book histograms and initialise projections before the run
31 void init() {
32
33 // Initialise and register projections
34
35 // the basic final-state projection:
36 // all final-state particles
37 const FinalState fs;
38
39 //get the final state b quarks for b-tagging
40 FinalPartons bquarks(Cuts::abspid == 5 && Cuts::pT > 5*GeV);
41 declare(bquarks, "bquarks");
42
43 // the final-state particles declared above are clustered using FastJet with
44 // the anti-kT algorithm and a jet-radius parameter 0.5
45 // muons and neutrinos are excluded from the clustering
46 FastJets jetfs(fs, JetAlg::ANTIKT, 0.5, JetMuons::NONE, JetInvisibles::NONE);
47 declare(jetfs, "jets");
48
49 // FinalState of bare muons and electrons in the event
50 Cut lepton_cuts = Cuts::pT>=20*GeV && Cuts::etaIn(2.0, 4.5);
51 FinalState fsmuons(Cuts::abspid == PID::MUON && lepton_cuts );
52 FinalState fselectrons(Cuts::abspid == PID::ELECTRON && lepton_cuts);
53
54 declare(fsmuons, "muons");
55 declare(fselectrons, "electrons");
56
57 // Inclusive cross-section measurement
58 book(_h_fiducial_xsect ,1,1,1);
59 }
60
61
62 /// Perform the per-event analysis
63 void analyze(const Event& event) {
64
65 // retrieve leptons, sorted by pT
66 const FinalState& muons = apply<FinalState>(event, "muons");
67 const FinalState& electrons = apply<FinalState>(event, "electrons");
68 const FinalPartons& bquarks = apply<FinalPartons>(event, "bquarks");
69
70 // retrieve clustered jets, sorted by pT, with a minimum pT cut
71 Jets jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 20*GeV && Cuts::etaIn(2.2,4.2));
72
73 if (jets.empty()) vetoEvent;
74 bool pass = false;
75 for (const auto& m : muons.particles()) {
76 for (const auto& e : electrons.particles()) {
77 if (deltaR(m.momentum(), e.momentum()) < 0.1 ) continue;
78 vector<Jet> lepton_jets;
79 for (const auto& j : jets ){
80 if (deltaR(j.momentum(), m.momentum()) > 0.5 &&
81 deltaR(j.momentum(), e.momentum()) > 0.5)
82 lepton_jets.push_back(j);
83 if (lepton_jets.size() > 0){
84 for (const auto& b : bquarks.particles()) {
85 if ( deltaR(b.momentum(), lepton_jets.at(0).momentum()) < 0.5 ) {
86 pass = true;
87 }
88 }
89 }
90 }
91 }
92 }
93
94 // veto event if it doesn't pass our selection
95 if (!pass) vetoEvent;
96 // append to cross-section
97 _h_fiducial_xsect->fill(13000);
98 }
99
100
101 /// Normalise histograms etc., after the run
102 void finalize() {
103 scale(_h_fiducial_xsect, crossSection()/femtobarn/sumOfWeights()); // norm to cross section
104 }
105
106
107 /// Histogram
108 BinnedHistoPtr<int> _h_fiducial_xsect;
109
110 };
111
112
113 RIVET_DECLARE_PLUGIN(LHCB_2018_I1662483);
114
115}
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