Rivet analyses referenceATLAS_2017_I1495243ttbar + jets at 13 TeVExperiment: ATLAS (LHC) Inspire ID: 1495243 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
Measurements of jet activity in top-quark pair events produced in proton--proton collisions are presented, using 3.2 fb$^{-1}$ of $pp$ collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events are chosen by requiring an opposite-charge $e\mu$ pair and two $b$-tagged jets in the final state. The normalised differential cross-sections of top-quark pair production are presented as functions of additional-jet multiplicity and transverse momentum, $p_\text{T}$. The fraction of signal events that do not contain additional jet activity in a given rapidity region, the gap fraction, is measured as a function of the $p_\text{T}$ threshold for additional jets, and is also presented for different invariant mass regions of the $e\mu b\bar{b}$ system. All measurements are corrected for detector effects and presented as particle-level distributions compared to predictions with different theoretical approaches for QCD radiation. While the kinematics of the jets from top-quark decays are described well, the generators show differing levels of agreement with the measurements of observables that depend on the production of additional jets. Source code: ATLAS_2017_I1495243.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/VetoedFinalState.hh"
4#include "Rivet/Projections/IdentifiedFinalState.hh"
5#include "Rivet/Projections/PromptFinalState.hh"
6#include "Rivet/Projections/LeptonFinder.hh"
7#include "Rivet/Projections/FastJets.hh"
8
9namespace Rivet {
10
11
12 /// @brief $t\bar{t}$ + jets at 13 TeV
13 class ATLAS_2017_I1495243 : public Analysis {
14 public:
15
16 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2017_I1495243);
17
18
19 void init() {
20
21 Cut eta_full = Cuts::abseta < 5.0 && Cuts::pT > 1.0*MeV;
22 Cut eta_lep = Cuts::abseta < 2.5;
23
24 // Collect final state particles
25 FinalState FS(eta_full);
26
27 // Get photons to dress leptons
28 IdentifiedFinalState photons(FS);
29 photons.acceptIdPair(PID::PHOTON);
30
31 // Projection to find the electrons
32 IdentifiedFinalState el_id(FS);
33 el_id.acceptIdPair(PID::ELECTRON);
34 PromptFinalState electrons(el_id);
35 electrons.acceptTauDecays(false);
36 LeptonFinder dressedelectrons(electrons, photons, 0.1, Cuts::abseta < 2.5 && Cuts::pT > 25*GeV);
37 declare(dressedelectrons, "electrons");
38 LeptonFinder fulldressedelectrons(electrons, photons, 0.1, eta_full);
39
40 // Projection to find the muons
41 IdentifiedFinalState mu_id(FS);
42 mu_id.acceptIdPair(PID::MUON);
43 PromptFinalState muons(mu_id);
44 muons.acceptTauDecays(false);
45 LeptonFinder dressedmuons(muons, photons, 0.1, Cuts::abseta < 2.5 && Cuts::pT > 25*GeV);
46 declare(dressedmuons, "muons");
47 LeptonFinder fulldressedmuons(muons, photons, 0.1, eta_full);
48
49 // Projection to find neutrinos to exclude from jets
50 IdentifiedFinalState nu_id;
51 nu_id.acceptNeutrinos();
52 PromptFinalState neutrinos(nu_id);
53 neutrinos.acceptTauDecays(false);
54
55 // Jet clustering
56 VetoedFinalState vfs;
57 vfs.addVetoOnThisFinalState(fulldressedelectrons);
58 vfs.addVetoOnThisFinalState(fulldressedmuons);
59 vfs.addVetoOnThisFinalState(neutrinos);
60 FastJets jets(vfs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::DECAY);
61 declare(jets, "jets");
62
63 // Book Histograms
64 book(_h["bjet_pt"] , 5,1,1);
65 book(_h["2bjet_pt"], 6,1,1);
66 book(_h["ljet_pt"] , 7,1,1);
67
68 for (size_t i = 0; i < 4; ++i) {
69 book(_h["njet" + to_str(i)], i+1, 1, 1);
70 book(_h["Q0" + to_str(i)], "_Q0" + to_str(i+ 7), refData((i>1?"d":"d0") + to_str(i+ 8) + "-x01-y01"));
71 book(_h["MQ0" + to_str(i)], "_MQ0" + to_str(i+12), refData("d" + to_str(i+12) + "-x01-y01"));
72 book(_h["Qsum" + to_str(i)], "_Qsum" + to_str(i+16), refData("d" + to_str(i+16) + "-x01-y01"));
73 book(_h["MQsum" + to_str(i)], "_MQsum" + to_str(i+20), refData("d" + to_str(i+20) + "-x01-y01"));
74 book(_s["gapFracQ0" + to_str(i)], 8+i, 1 ,1);
75 book(_s["gapFracMQ0" + to_str(i)], 12+i, 1, 1);
76 book(_s["gapFracQsum" + to_str(i)], 16+i, 1, 1);
77 book(_s["gapFracMQsum" + to_str(i)], 20+i, 1, 1);
78 }
79 }
80
81
82 void analyze(const Event& event) {
83
84 // Get the selected objects, using the projections.
85 Jets all_jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 2.5);
86
87 const DressedLeptons electrons = discard(apply<LeptonFinder>(event, "electrons").dressedLeptons(),
88 [&](const DressedLepton &e) {
89 return any(all_jets, deltaRLess(e, 0.4));
90 });
91
92 const DressedLeptons muons = discard(apply<LeptonFinder>(event, "muons").dressedLeptons(),
93 [&](const DressedLepton &m) {
94 return any(all_jets, deltaRLess(m, 0.4));
95 });
96
97 if (electrons.size() != 1 || muons.size() != 1) vetoEvent;
98 if (electrons[0].charge() == muons[0].charge()) vetoEvent;
99
100 Jets bjets, extrajets;
101 for (Jet j : all_jets) {
102 size_t b_tagged = j.bTags(Cuts::pT > 5*GeV).size();
103 if (bjets.size() < 2 && b_tagged) bjets += j;
104 else extrajets += j;
105 }
106 if (bjets.size() < 2) vetoEvent;
107
108 double bjetpt = bjets[0].pt();
109 if (bjetpt > 250*GeV) bjetpt = 275*GeV;
110 _h["bjet_pt"]->fill(bjetpt);
111
112 double b2jetpt = bjets[1].pt();
113 if (b2jetpt > 150*GeV) b2jetpt = 175*GeV;
114 _h["2bjet_pt"]->fill(b2jetpt);
115
116 if (extrajets.size()) {
117 double ljetpt = extrajets[0].pt();
118 if (ljetpt > 250*GeV) ljetpt = 275*GeV;
119 _h["ljet_pt"]->fill(ljetpt);
120 }
121
122 double Memubb = (electrons[0].momentum() + muons[0].momentum() + bjets[0].momentum() + bjets[1].momentum()).mass();
123 vector<double> leadpt = { 0., 0., 0., 0. }, ptsum = { 0., 0., 0., 0. };
124 vector<size_t> njetcount = { 0, 0, 0, 0 };
125 for (size_t i = 0; i < extrajets.size(); ++i) {
126 double absrap = extrajets[i].absrap(), pt = extrajets[i].pT();
127 if (pt > 25*GeV) ++njetcount[0];
128 if (pt > 40*GeV) ++njetcount[1];
129 if (pt > 60*GeV) ++njetcount[2];
130 if (pt > 80*GeV) ++njetcount[3];
131
132 if (absrap < 0.8 && pt > leadpt[0]) leadpt[0] = pt;
133 else if (absrap > 0.8 && absrap < 1.5 && pt > leadpt[1]) leadpt[1] = pt;
134 else if (absrap > 1.5 && absrap < 2.1 && pt > leadpt[2]) leadpt[2] = pt;
135 if (absrap < 2.1 && pt > leadpt[3]) leadpt[3] = pt;
136
137 if (absrap < 0.8) ptsum[0] += pt;
138 else if (absrap > 0.8 && absrap < 1.5) ptsum[1] += pt;
139 else if (absrap > 1.5 && absrap < 2.1) ptsum[2] += pt;
140 if (absrap < 2.1) ptsum[3] += pt;
141 }
142
143
144 for (size_t i = 0; i < 4; ++i) {
145 size_t cutoff = i? 3 : 4;
146 if (njetcount[i] > cutoff) njetcount[i] = cutoff;
147 _h["njet" + to_str(i)]->fill(njetcount[i]);
148
149 if (leadpt[i] > 305*GeV) leadpt[i] = 305*GeV;
150 _h["Q0" + to_str(i)]->fill(leadpt[i]);
151
152 if (ptsum[i] > 505*GeV) ptsum[i] = 505*GeV;
153 _h["Qsum" + to_str(i)]->fill(ptsum[i]);
154 }
155
156
157 for (size_t i = 0; i < 4; ++i) {
158 if (i == 0 && !(Memubb < 300*GeV)) continue;
159 if (i == 1 && !(Memubb > 300*GeV && Memubb < 425*GeV)) continue;
160 if (i == 2 && !(Memubb > 425*GeV && Memubb < 600*GeV)) continue;
161 if (i == 3 && !(Memubb > 600*GeV)) continue;
162 _h["MQ0" + to_str(i)]->fill(leadpt[3]);
163 _h["MQsum" + to_str(i)]->fill(ptsum[3]);
164 }
165 }
166
167
168 void constructGapFraction(Estimate1DPtr out, Histo1DPtr in) {
169 bool hasWeights = in->effNumEntries() != in->numEntries();
170 double denW = in->sumW();
171 double denW2 = in->sumW2();
172 size_t nEnd = out->numBins();
173
174 for (auto& b : out->bins()) {
175 double numW = in->sumW(), numW2 = in->sumW2();
176 for (size_t j = b.index(); j < nEnd; ++j) {
177 numW -= in->bin(j).sumW();
178 numW2 -= in->bin(j).sumW2();
179 }
180 double yval = safediv(numW, denW);
181 double yerr = sqrt(safediv(yval * (1 - yval), denW));
182 if (hasWeights) { // use F. James's approximation for weighted events
183 yerr = sqrt( safediv((1 - 2 * yval) * numW2 + yval * yval * denW2, denW * denW) );
184 }
185 b.set(yval, yerr);
186 }
187 }
188
189
190 void finalize() {
191
192 // Build gap fraction plots
193 for (size_t i = 0; i < 4; ++i) {
194 constructGapFraction(_s["gapFracQ0" + to_str(i)], _h["Q0" + to_str(i)]);
195 constructGapFraction(_s["gapFracMQ0" + to_str(i)], _h["MQ0" + to_str(i)]);
196 constructGapFraction(_s["gapFracQsum" + to_str(i)], _h["Qsum" + to_str(i)]);
197 constructGapFraction(_s["gapFracMQsum" + to_str(i)], _h["MQsum" + to_str(i)]);
198 }
199
200 // Normalize to cross-section
201 for (map<string, Histo1DPtr>::iterator hit = _h.begin(); hit != _h.end(); ++hit) {
202 if (hit->first.find("jet") != string::npos) normalize(hit->second);
203 }
204 }
205
206
207 private:
208
209 /// @name Histogram helper functions
210 map<string, Histo1DPtr> _h;
211 map<string, Estimate1DPtr> _s;
212 };
213
214
215 RIVET_DECLARE_PLUGIN(ATLAS_2017_I1495243);
216
217
218}
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