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/DressedLeptons.hh"
5#include "Rivet/Projections/PromptFinalState.hh"
6#include "Rivet/Projections/VetoedFinalState.hh"
7
8namespace Rivet {
9
10
11/// @brief ttbb at 13 TeV
12class ATLAS_2018_I1705857 : public Analysis {
13 public:
14 /// Constructor
15 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2018_I1705857);
16
17 void init() {
18 // Eta ranges
19 Cut eta_full = (Cuts::abseta < 5.0);
20 // Lepton cuts
21 Cut lep_cuts25 = (Cuts::abseta < 2.5) && (Cuts::pT >= 25*GeV);
22 // All final state particles
23 FinalState fs(eta_full);
24
25 // Get photons to dress leptons
26 PromptFinalState photons(eta_full && Cuts::abspid == PID::PHOTON, true);
27
28 // Projection to find the electrons
29 PromptFinalState electrons(eta_full && Cuts::abspid == PID::ELECTRON, true);
30
31 // Projection to find the muons
32 PromptFinalState muons(eta_full && Cuts::abspid == PID::MUON, true);
33
34 DressedLeptons dressedelectrons25(photons, electrons, 0.1, lep_cuts25, true);
35 DressedLeptons dressedmuons25(photons, muons, 0.1, lep_cuts25, true);
36
37 declare(dressedelectrons25, "elecs");
38 declare(dressedmuons25, "muons");
39
40 // From here on we are just setting up the jet clustering
41 IdentifiedFinalState nu_id;
42 nu_id.acceptNeutrinos();
43 PromptFinalState neutrinos(nu_id);
44 neutrinos.acceptTauDecays(true);
45
46 PromptFinalState jet_photons(eta_full && Cuts::abspid == PID::PHOTON, false);
47 DressedLeptons all_dressed_electrons(jet_photons, electrons, 0.1, eta_full, true);
48 DressedLeptons all_dressed_muons(jet_photons, muons, 0.1, eta_full, true);
49
50 VetoedFinalState vfs(fs);
51 vfs.addVetoOnThisFinalState(all_dressed_electrons);
52 vfs.addVetoOnThisFinalState(all_dressed_muons);
53 vfs.addVetoOnThisFinalState(neutrinos);
54
55 FastJets jets(vfs, FastJets::ANTIKT, 0.4, JetAlg::Muons::DECAY, JetAlg::Invisibles::DECAY);
56 declare(jets, "jets");
57
58 // fiducial cross-section histogram
59 book(_histograms["fid_xsec"], 1, 1, 1);
60 book(_histograms["fid_xsec_no_ttX"], 2, 1, 1);
61
62 book(_histograms["nbjets_emu"], 3, 1, 1);
63 book(_histograms["nbjets_emu_no_ttX"], 4, 1, 1);
64
65 // HT
66 book_hist("ht_emu", 3);
67 book_hist("ht_had_emu", 4);
68
69 book_hist("ht_ljets", 5);
70 book_hist("ht_had_ljets", 6);
71
72 // b-jet pTs
73 book_hist("lead_bjet_pt_emu", 7);
74 book_hist("sublead_bjet_pt_emu", 8);
75 book_hist("third_bjet_pt_emu", 9);
76
77 book_hist("lead_bjet_pt_ljets", 10);
78 book_hist("sublead_bjet_pt_ljets", 11);
79 book_hist("third_bjet_pt_ljets", 12);
80 book_hist("fourth_bjet_pt_ljets", 13);
81
82 // leading bb pair
83 book_hist("m_bb_leading_emu", 14);
84 book_hist("pt_bb_leading_emu", 15);
85 book_hist("dR_bb_leading_emu", 16);
86
87 book_hist("m_bb_leading_ljets", 17);
88 book_hist("pt_bb_leading_ljets", 18);
89 book_hist("dR_bb_leading_ljets", 19);
90
91 // closest bb pair
92 book_hist("m_bb_closest_emu", 20);
93 book_hist("pt_bb_closest_emu", 21);
94 book_hist("dR_bb_closest_emu", 22);
95
96 book_hist("m_bb_closest_ljets", 23);
97 book_hist("pt_bb_closest_ljets", 24);
98 book_hist("dR_bb_closest_ljets", 25);
99 }
100
101
102 void analyze(const Event& event) {
103
104 vector<DressedLepton> leptons;
105 for (auto &lep : apply<DressedLeptons>(event, "muons").dressedLeptons()) { leptons.push_back(lep); }
106 for (auto &lep : apply<DressedLeptons>(event, "elecs").dressedLeptons()) { leptons.push_back(lep); }
107
108 const Jets jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 2.5);
109 for (const auto& jet : jets) {
110 ifilter_discard(leptons, [&](const DressedLepton& lep) { return deltaR(jet, lep) < 0.4; });
111 }
112
113 Jets bjets;
114 for (const Jet& jet : jets) {
115 if (jet.bTagged(Cuts::pT >= 5*GeV)) bjets += jet;
116 }
117
118 size_t njets = jets.size();
119 size_t nbjets = bjets.size();
120
121 // Evaluate basic event selection
122 bool pass_ljets = (leptons.size() == 1 && leptons[0].pT() > 27*GeV);
123
124 bool pass_emu =
125 // 2 leptons > 27 GeV
126 (leptons.size() == 2) &&
127 (leptons[0].pT() > 27*GeV && leptons[1].pT() > 27*GeV) &&
128 // emu events
129 ((leptons[0].abspid() == 11 && leptons[1].abspid() == 13) ||
130 (leptons[0].abspid() == 13 && leptons[1].abspid() == 11)) &&
131 // opposite charge
132 (leptons[0].charge() != leptons[1].charge());
133
134 // If we don't have exactly 1 or 2 leptons then veto the event
135 if (!pass_emu && !pass_ljets) vetoEvent;
136
137 if (pass_emu) {
138 if (nbjets >= 2) fill("nbjets_emu", nbjets - 1);
139 if (nbjets >= 3) fill("fid_xsec", 1);
140 if (nbjets >= 4) fill("fid_xsec", 2);
141 }
142
143 if (pass_ljets) {
144 if (nbjets >= 3 && njets >= 5) fill("fid_xsec", 3);
145 if (nbjets >= 4 && njets >= 6) fill("fid_xsec", 4);
146 }
147
148 if (pass_emu && (nbjets < 3 || njets < 3)) vetoEvent;
149 if (pass_ljets && (nbjets < 4 || njets < 6)) vetoEvent;
150
151 double hthad = sum(jets, pT, 0.0);
152 double ht = sum(leptons, pT, hthad);
153
154 FourMomentum jsum = bjets[0].momentum() + bjets[1].momentum();
155 double dr_leading = deltaR(bjets[0], bjets[1]);
156
157 size_t ind1 = 0, ind2 = 0; double mindr = 999.;
158 for (size_t i = 0; i < bjets.size(); ++i) {
159 for (size_t j = 0; j < bjets.size(); ++j) {
160 if (i == j) continue;
161 double dr = deltaR(bjets[i], bjets[j]);
162 if (dr < mindr) {
163 ind1 = i;
164 ind2 = j;
165 mindr = dr;
166 }
167 }
168 }
169
170 FourMomentum bb_closest = bjets[ind1].momentum() + bjets[ind2].momentum();
171 double dr_closest = deltaR(bjets[ind1], bjets[ind2]);
172
173 if (pass_ljets) {
174 // b-jet pTs
175 fill("lead_bjet_pt_ljets", bjets[0].pT()/GeV);
176 fill("sublead_bjet_pt_ljets", bjets[1].pT()/GeV);
177 fill("third_bjet_pt_ljets", bjets[2].pT()/GeV);
178
179 if (nbjets >= 4) fill("fourth_bjet_pt_ljets", bjets[3].pT()/GeV);
180
181 // HT
182 fill("ht_ljets", ht/GeV);
183 fill("ht_had_ljets", hthad/GeV);
184
185 // leading bb pair
186 fill("m_bb_leading_ljets", jsum.mass()/GeV);
187 fill("pt_bb_leading_ljets", jsum.pT()/GeV);
188 fill("dR_bb_leading_ljets", dr_leading);
189
190 // closest bb pair
191 fill("m_bb_closest_ljets", bb_closest.mass()/GeV);
192 fill("pt_bb_closest_ljets", bb_closest.pT()/GeV);
193 fill("dR_bb_closest_ljets", dr_closest);
194 }
195 if (pass_emu) {
196 // b-jet pTs
197 fill("lead_bjet_pt_emu", bjets[0].pT()/GeV);
198 fill("sublead_bjet_pt_emu", bjets[1].pT()/GeV);
199 fill("third_bjet_pt_emu", bjets[2].pT()/GeV);
200
201 // HT
202 fill("ht_emu", ht/GeV);
203 fill("ht_had_emu", hthad/GeV);
204
205 // leading bb pair
206 fill("m_bb_leading_emu", jsum.mass()/GeV);
207 fill("pt_bb_leading_emu", jsum.pT()/GeV);
208 fill("dR_bb_leading_emu", dr_leading);
209
210 // closest bb pair
211 fill("m_bb_closest_emu", bb_closest.mass()/GeV);
212 fill("pt_bb_closest_emu", bb_closest.pT()/GeV);
213 fill("dR_bb_closest_emu", dr_closest);
214 }
215 }
216
217 void finalize() {
218 // Normalise all histograms
219 const double sf = crossSection() / femtobarn / sumOfWeights();
220 for (auto const& h : _histograms) {
221 scale(h.second, sf);
222 if (h.first.find("fid_xsec") != string::npos) continue;
223 normalize(h.second, 1.0);
224 }
225 }
226
227 void fill(const string& name, const double value) {
228 _histograms[name]->fill(value);
229 _histograms[name + "_no_ttX"]->fill(value);
230 }
231
232 void book_hist(const std::string& name, unsigned int d) {
233 // ttX substracted histograms are even numbers
234 book(_histograms[name], (d * 2) - 1, 1, 1);
235 book(_histograms[name + "_no_ttX"], d * 2, 1, 1);
236 }
237
238 private:
239 map<std::string, Histo1DPtr> _histograms;
240
241 };
242
243 // The hook for the plugin system
244 RIVET_DECLARE_PLUGIN(ATLAS_2018_I1705857);
245}
|