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(_d["nbjets_emu"], 3, 1, 1);
65 book(_d["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 DressedLeptons leptons;
106 for (auto &lep : apply<LeptonFinder>(event, "muons").dressedLeptons()) { leptons.push_back(lep); }
107 for (auto &lep : apply<LeptonFinder>(event, "elecs").dressedLeptons()) { leptons.push_back(lep); }
108
109 const Jets jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 2.5);
110 for (const auto& jet : jets) {
111 idiscard(leptons, [&](const DressedLepton& lep) { return deltaR(jet, lep) < 0.4; });
112 }
113
114 Jets bjets;
115 for (const Jet& jet : jets) {
116 if (jet.bTagged(Cuts::pT >= 5*GeV)) bjets += jet;
117 }
118
119 size_t njets = jets.size();
120 size_t nbjets = bjets.size();
121
122 // Evaluate basic event selection
123 bool pass_ljets = (leptons.size() == 1 && leptons[0].pT() > 27*GeV);
124
125 bool pass_emu =
126 // 2 leptons > 27 GeV
127 (leptons.size() == 2) &&
128 (leptons[0].pT() > 27*GeV && leptons[1].pT() > 27*GeV) &&
129 // emu events
130 ((leptons[0].abspid() == 11 && leptons[1].abspid() == 13) ||
131 (leptons[0].abspid() == 13 && leptons[1].abspid() == 11)) &&
132 // opposite charge
133 (leptons[0].charge() != leptons[1].charge());
134
135 // If we don't have exactly 1 or 2 leptons then veto the event
136 if (!pass_emu && !pass_ljets) vetoEvent;
137
138 if (pass_emu) {
139 if (nbjets >= 2) dfill("nbjets_emu", nbjets);
140 if (nbjets >= 3) fill("fid_xsec", 1);
141 if (nbjets >= 4) fill("fid_xsec", 2);
142 }
143
144 if (pass_ljets) {
145 if (nbjets >= 3 && njets >= 5) fill("fid_xsec", 3);
146 if (nbjets >= 4 && njets >= 6) fill("fid_xsec", 4);
147 }
148
149 if (pass_emu && (nbjets < 3 || njets < 3)) vetoEvent;
150 if (pass_ljets && (nbjets < 4 || njets < 6)) vetoEvent;
151
152 double hthad = sum(jets, Kin::pT, 0.0);
153 double ht = sum(leptons, Kin::pT, hthad);
154
155 FourMomentum jsum = bjets[0].momentum() + bjets[1].momentum();
156 double dr_leading = deltaR(bjets[0], bjets[1]);
157
158 size_t ind1 = 0, ind2 = 0; double mindr = 999.;
159 for (size_t i = 0; i < bjets.size(); ++i) {
160 for (size_t j = 0; j < bjets.size(); ++j) {
161 if (i == j) continue;
162 double dr = deltaR(bjets[i], bjets[j]);
163 if (dr < mindr) {
164 ind1 = i;
165 ind2 = j;
166 mindr = dr;
167 }
168 }
169 }
170
171 FourMomentum bb_closest = bjets[ind1].momentum() + bjets[ind2].momentum();
172 double dr_closest = deltaR(bjets[ind1], bjets[ind2]);
173
174 if (pass_ljets) {
175 // b-jet pTs
176 fill("lead_bjet_pt_ljets", bjets[0].pT()/GeV);
177 fill("sublead_bjet_pt_ljets", bjets[1].pT()/GeV);
178 fill("third_bjet_pt_ljets", bjets[2].pT()/GeV);
179
180 if (nbjets >= 4) fill("fourth_bjet_pt_ljets", bjets[3].pT()/GeV);
181
182 // HT
183 fill("ht_ljets", ht/GeV);
184 fill("ht_had_ljets", hthad/GeV);
185
186 // leading bb pair
187 fill("m_bb_leading_ljets", jsum.mass()/GeV);
188 fill("pt_bb_leading_ljets", jsum.pT()/GeV);
189 fill("dR_bb_leading_ljets", dr_leading);
190
191 // closest bb pair
192 fill("m_bb_closest_ljets", bb_closest.mass()/GeV);
193 fill("pt_bb_closest_ljets", bb_closest.pT()/GeV);
194 fill("dR_bb_closest_ljets", dr_closest);
195 }
196 if (pass_emu) {
197 // b-jet pTs
198 fill("lead_bjet_pt_emu", bjets[0].pT()/GeV);
199 fill("sublead_bjet_pt_emu", bjets[1].pT()/GeV);
200 fill("third_bjet_pt_emu", bjets[2].pT()/GeV);
201
202 // HT
203 fill("ht_emu", ht/GeV);
204 fill("ht_had_emu", hthad/GeV);
205
206 // leading bb pair
207 fill("m_bb_leading_emu", jsum.mass()/GeV);
208 fill("pt_bb_leading_emu", jsum.pT()/GeV);
209 fill("dR_bb_leading_emu", dr_leading);
210
211 // closest bb pair
212 fill("m_bb_closest_emu", bb_closest.mass()/GeV);
213 fill("pt_bb_closest_emu", bb_closest.pT()/GeV);
214 fill("dR_bb_closest_emu", dr_closest);
215 }
216 }
217
218 void finalize() {
219 // Normalise all histograms
220 const double sf = crossSection() / femtobarn / sumOfWeights();
221 for (auto& h : _histograms) {
222 scale(h.second, sf);
223 if (h.first.find("fid_xsec") != string::npos) continue;
224 normalize(h.second, 1.0);
225 }
226 scale(_d, sf);
227 normalize(_d["nbjets_emu"]);
228 normalize(_d["nbjets_emu_no_ttX"]);
229 }
230
231 void fill(const string& name, const double value) {
232 _histograms[name]->fill(value);
233 _histograms[name + "_no_ttX"]->fill(value);
234 }
235
236 void dfill(const string& name, const size_t value) {
237 string edge("OTHER");
238 if (value == 2) edge = "2";
239 else if (value == 3) edge = "3";
240 else if (value >= 4) edge = ">= 4";
241 _d[name]->fill(edge);
242 _d[name + "_no_ttX"]->fill(edge);
243 }
244
245 void book_hist(const std::string& name, unsigned int d) {
246 // ttX substracted histograms are even numbers
247 book(_histograms[name], (d * 2) - 1, 1, 1);
248 book(_histograms[name + "_no_ttX"], d * 2, 1, 1);
249 }
250
251 private:
252 map<std::string, Histo1DPtr> _histograms;
253 map<std::string, BinnedHistoPtr<string>> _d;
254
255 };
256
257 RIVET_DECLARE_PLUGIN(ATLAS_2018_I1705857);
258}
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