Rivet analyses referenceATLAS_2018_I1705857ttbb at 13 TeVExperiment: ATLAS (LHC) Inspire ID: 1705857 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
This paper presents measurements of $t\bar{t}$ production in association with additional $b$-jets in $pp$ collisions at the LHC at a centre-of-mass energy of 13 TeV. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 36.1 fb$^{-1}$. Fiducial cross-section measurements are performed in the dilepton and lepton-plus-jets $t\bar{t}$ decay channels. Results are presented at particle level in the form of inclusive cross-sections of $t\bar{t}$ final states with three and four $b$-jets as well as differential cross-sections as a function of global event properties and properties of $b$-jet pairs. The measured inclusive fiducial cross-sections generally exceed the $t\bar{t}b\bar{b}$ predictions from various next-to-leading-order matrix element calculations matched to a parton shower but are compatible within the total uncertainties. The experimental uncertainties are smaller than the uncertainties in the predictions. Comparisons of state-of-the-art theoretical predictions with the differential measurements are shown and good agreement with data is found for most of them. Source code: ATLAS_2018_I1705857.cc 1#include "Rivet/Analysis.hh"
2#include "Rivet/Projections/FastJets.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/LeptonFinder.hh"
5#include "Rivet/Projections/PromptFinalState.hh"
6#include "Rivet/Projections/VetoedFinalState.hh"
7
8namespace Rivet {
9
10
11 /// ttbb at 13 TeV
12 class ATLAS_2018_I1705857 : public Analysis {
13 public:
14
15 /// Constructor
16 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2018_I1705857);
17
18
19 void init() {
20 // Eta ranges
21 Cut eta_full = (Cuts::abseta < 5.0);
22 // Lepton cuts
23 Cut lep_cuts25 = (Cuts::abseta < 2.5) && (Cuts::pT >= 25*GeV);
24 // All final state particles
25 FinalState fs(eta_full);
26
27 // Get photons to dress leptons
28 PromptFinalState photons(eta_full && Cuts::abspid == PID::PHOTON, TauDecaysAs::PROMPT);
29
30 // Projection to find the electrons
31 PromptFinalState electrons(eta_full && Cuts::abspid == PID::ELECTRON, TauDecaysAs::PROMPT);
32
33 // Projection to find the muons
34 PromptFinalState muons(eta_full && Cuts::abspid == PID::MUON, TauDecaysAs::PROMPT);
35
36 LeptonFinder dressedelectrons25(electrons, photons, 0.1, lep_cuts25);
37 LeptonFinder dressedmuons25(muons, photons, 0.1, lep_cuts25);
38
39 declare(dressedelectrons25, "elecs");
40 declare(dressedmuons25, "muons");
41
42 // From here on we are just setting up the jet clustering
43 IdentifiedFinalState nu_id;
44 nu_id.acceptNeutrinos();
45 PromptFinalState neutrinos(nu_id);
46 neutrinos.acceptTauDecays(true);
47
48 PromptFinalState jet_photons(eta_full && Cuts::abspid == PID::PHOTON, TauDecaysAs::NONPROMPT);
49 LeptonFinder all_dressed_electrons(electrons, jet_photons, 0.1, eta_full);
50 LeptonFinder all_dressed_muons(muons, jet_photons, 0.1, eta_full);
51
52 VetoedFinalState vfs(fs);
53 vfs.addVetoOnThisFinalState(all_dressed_electrons);
54 vfs.addVetoOnThisFinalState(all_dressed_muons);
55 vfs.addVetoOnThisFinalState(neutrinos);
56
57 FastJets jets(vfs, JetAlg::ANTIKT, 0.4, JetMuons::DECAY, JetInvisibles::DECAY);
58 declare(jets, "jets");
59
60 // fiducial cross-section histogram
61 book(_histograms["fid_xsec"], 1, 1, 1);
62 book(_histograms["fid_xsec_no_ttX"], 2, 1, 1);
63
64 book(_histograms["nbjets_emu"], 3, 1, 1);
65 book(_histograms["nbjets_emu_no_ttX"], 4, 1, 1);
66
67 // HT
68 book_hist("ht_emu", 3);
69 book_hist("ht_had_emu", 4);
70
71 book_hist("ht_ljets", 5);
72 book_hist("ht_had_ljets", 6);
73
74 // b-jet pTs
75 book_hist("lead_bjet_pt_emu", 7);
76 book_hist("sublead_bjet_pt_emu", 8);
77 book_hist("third_bjet_pt_emu", 9);
78
79 book_hist("lead_bjet_pt_ljets", 10);
80 book_hist("sublead_bjet_pt_ljets", 11);
81 book_hist("third_bjet_pt_ljets", 12);
82 book_hist("fourth_bjet_pt_ljets", 13);
83
84 // leading bb pair
85 book_hist("m_bb_leading_emu", 14);
86 book_hist("pt_bb_leading_emu", 15);
87 book_hist("dR_bb_leading_emu", 16);
88
89 book_hist("m_bb_leading_ljets", 17);
90 book_hist("pt_bb_leading_ljets", 18);
91 book_hist("dR_bb_leading_ljets", 19);
92
93 // closest bb pair
94 book_hist("m_bb_closest_emu", 20);
95 book_hist("pt_bb_closest_emu", 21);
96 book_hist("dR_bb_closest_emu", 22);
97
98 book_hist("m_bb_closest_ljets", 23);
99 book_hist("pt_bb_closest_ljets", 24);
100 book_hist("dR_bb_closest_ljets", 25);
101 }
102
103
104 void analyze(const Event& event) {
105
106 DressedLeptons leptons;
107 for (auto &lep : apply<LeptonFinder>(event, "muons").dressedLeptons()) { leptons.push_back(lep); }
108 for (auto &lep : apply<LeptonFinder>(event, "elecs").dressedLeptons()) { leptons.push_back(lep); }
109
110 const Jets jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 2.5);
111 for (const auto& jet : jets) {
112 idiscard(leptons, [&](const DressedLepton& lep) { return deltaR(jet, lep) < 0.4; });
113 }
114
115 Jets bjets;
116 for (const Jet& jet : jets) {
117 if (jet.bTagged(Cuts::pT >= 5*GeV)) bjets += jet;
118 }
119
120 size_t njets = jets.size();
121 size_t nbjets = bjets.size();
122
123 // Evaluate basic event selection
124 bool pass_ljets = (leptons.size() == 1 && leptons[0].pT() > 27*GeV);
125
126 bool pass_emu =
127 // 2 leptons > 27 GeV
128 (leptons.size() == 2) &&
129 (leptons[0].pT() > 27*GeV && leptons[1].pT() > 27*GeV) &&
130 // emu events
131 ((leptons[0].abspid() == 11 && leptons[1].abspid() == 13) ||
132 (leptons[0].abspid() == 13 && leptons[1].abspid() == 11)) &&
133 // opposite charge
134 (leptons[0].charge() != leptons[1].charge());
135
136 // If we don't have exactly 1 or 2 leptons then veto the event
137 if (!pass_emu && !pass_ljets) vetoEvent;
138
139 if (pass_emu) {
140 if (nbjets >= 2) fill("nbjets_emu", nbjets - 1);
141 if (nbjets >= 3) fill("fid_xsec", 1);
142 if (nbjets >= 4) fill("fid_xsec", 2);
143 }
144
145 if (pass_ljets) {
146 if (nbjets >= 3 && njets >= 5) fill("fid_xsec", 3);
147 if (nbjets >= 4 && njets >= 6) fill("fid_xsec", 4);
148 }
149
150 if (pass_emu && (nbjets < 3 || njets < 3)) vetoEvent;
151 if (pass_ljets && (nbjets < 4 || njets < 6)) vetoEvent;
152
153 double hthad = sum(jets, Kin::pT, 0.0);
154 double ht = sum(leptons, Kin::pT, hthad);
155
156 FourMomentum jsum = bjets[0].momentum() + bjets[1].momentum();
157 double dr_leading = deltaR(bjets[0], bjets[1]);
158
159 size_t ind1 = 0, ind2 = 0; double mindr = 999.;
160 for (size_t i = 0; i < bjets.size(); ++i) {
161 for (size_t j = 0; j < bjets.size(); ++j) {
162 if (i == j) continue;
163 double dr = deltaR(bjets[i], bjets[j]);
164 if (dr < mindr) {
165 ind1 = i;
166 ind2 = j;
167 mindr = dr;
168 }
169 }
170 }
171
172 FourMomentum bb_closest = bjets[ind1].momentum() + bjets[ind2].momentum();
173 double dr_closest = deltaR(bjets[ind1], bjets[ind2]);
174
175 if (pass_ljets) {
176 // b-jet pTs
177 fill("lead_bjet_pt_ljets", bjets[0].pT()/GeV);
178 fill("sublead_bjet_pt_ljets", bjets[1].pT()/GeV);
179 fill("third_bjet_pt_ljets", bjets[2].pT()/GeV);
180
181 if (nbjets >= 4) fill("fourth_bjet_pt_ljets", bjets[3].pT()/GeV);
182
183 // HT
184 fill("ht_ljets", ht/GeV);
185 fill("ht_had_ljets", hthad/GeV);
186
187 // leading bb pair
188 fill("m_bb_leading_ljets", jsum.mass()/GeV);
189 fill("pt_bb_leading_ljets", jsum.pT()/GeV);
190 fill("dR_bb_leading_ljets", dr_leading);
191
192 // closest bb pair
193 fill("m_bb_closest_ljets", bb_closest.mass()/GeV);
194 fill("pt_bb_closest_ljets", bb_closest.pT()/GeV);
195 fill("dR_bb_closest_ljets", dr_closest);
196 }
197 if (pass_emu) {
198 // b-jet pTs
199 fill("lead_bjet_pt_emu", bjets[0].pT()/GeV);
200 fill("sublead_bjet_pt_emu", bjets[1].pT()/GeV);
201 fill("third_bjet_pt_emu", bjets[2].pT()/GeV);
202
203 // HT
204 fill("ht_emu", ht/GeV);
205 fill("ht_had_emu", hthad/GeV);
206
207 // leading bb pair
208 fill("m_bb_leading_emu", jsum.mass()/GeV);
209 fill("pt_bb_leading_emu", jsum.pT()/GeV);
210 fill("dR_bb_leading_emu", dr_leading);
211
212 // closest bb pair
213 fill("m_bb_closest_emu", bb_closest.mass()/GeV);
214 fill("pt_bb_closest_emu", bb_closest.pT()/GeV);
215 fill("dR_bb_closest_emu", dr_closest);
216 }
217 }
218
219 void finalize() {
220 // Normalise all histograms
221 const double sf = crossSection() / femtobarn / sumOfWeights();
222 for (auto& h : _histograms) {
223 scale(h.second, sf);
224 if (h.first.find("fid_xsec") != string::npos) continue;
225 normalize(h.second, 1.0);
226 }
227 }
228
229 void fill(const string& name, const double value) {
230 _histograms[name]->fill(value);
231 _histograms[name + "_no_ttX"]->fill(value);
232 }
233
234 void book_hist(const std::string& name, unsigned int d) {
235 // ttX substracted histograms are even numbers
236 book(_histograms[name], (d * 2) - 1, 1, 1);
237 book(_histograms[name + "_no_ttX"], d * 2, 1, 1);
238 }
239
240 private:
241 map<std::string, Histo1DPtr> _histograms;
242
243 };
244
245 RIVET_DECLARE_PLUGIN(ATLAS_2018_I1705857);
246}
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