Rivet analyses referenceATLAS_2018_I1677498WWbb at 13 TeVExperiment: ATLAS (LHC) Inspire ID: 1677498 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a $W$ boson and a $b$-quark are significant. Events with exactly two leptons ($ee$, $\mu\mu$, or $e\mu$) and two $b$-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb$^{-1}$ of proton-proton collision data taken at $\sqrt{s}=13$ TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within $2\sigma$ of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning. Source code: ATLAS_2018_I1677498.cc 1#include "Rivet/Analysis.hh"
2#include "Rivet/Projections/FinalState.hh"
3#include "Rivet/Projections/PromptFinalState.hh"
4#include "Rivet/Projections/DressedLeptons.hh"
5#include "Rivet/Projections/FastJets.hh"
6
7namespace Rivet {
8
9
10 /// WWbb at 13 TeV
11 class ATLAS_2018_I1677498 : public Analysis {
12 public:
13
14 /// Constructor
15 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2018_I1677498);
16
17
18 /// Book cuts and projections
19 void init() {
20
21 // All final state particles
22 FinalState fs(Cuts::abseta < 5.0);
23
24 PromptFinalState photons(Cuts::abspid == PID::PHOTON, true); // true accepts tau decays
25
26 PromptFinalState bare_el(Cuts::abspid == PID::ELECTRON, true); // true accepts tau decays
27 DressedLeptons elecs(photons, bare_el, 0.1, Cuts::pT > 7*GeV && Cuts::abseta < 2.47);
28 declare(elecs, "elecs");
29
30 PromptFinalState bare_mu(Cuts::abspid == PID::MUON, true); // accepts tau decays
31 DressedLeptons muons(photons, bare_mu, 0.1, Cuts::pT > 6*GeV && Cuts::abseta < 2.5);
32 declare(muons, "muons");
33
34 FastJets jets(fs, FastJets::ANTIKT, 0.4, JetAlg::Muons::NONE, JetAlg::Invisibles::NONE);
35 declare(jets, "jets");
36
37 book(_h, 3, 1, 1);
38 }
39
40
41 void analyze(const Event& event) {
42
43 // Identify bjets (signal), light jets (OR) and soft b-jets (veto)
44 size_t soft_bjets = 0;
45 Jets bjets, lightjets;
46 for (const Jet& jet : apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 5*GeV)) {
47 bool isBjet = jet.bTagged(Cuts::pT > 5*GeV);
48 if (isBjet) soft_bjets += 1;
49 if (jet.abseta() < 2.5) {
50 if ( isBjet && jet.pT() > 25*GeV) bjets += jet;
51 if (!isBjet && jet.pT() > 20*GeV) lightjets += jet;
52 }
53 }
54 if (soft_bjets != 2) vetoEvent;
55 if (bjets.size() != 2) vetoEvent;
56
57 // Get dressed leptons
58 vector<DressedLepton> leptons;
59 for (auto& lep : apply<DressedLeptons>(event, "muons").dressedLeptons()) { leptons.push_back(lep); }
60 for (auto& lep : apply<DressedLeptons>(event, "elecs").dressedLeptons()) { leptons.push_back(lep); }
61
62 // 1. Find which light jets survive OR
63 for (const auto& lep : leptons) {
64 ifilter_discard(lightjets, [&](const Jet& jet) {
65 return deltaR(jet, lep) < 0.2 && (lep.abspid() == PID::ELECTRON || lep.pT()/jet.pT() > 0.7);
66 });
67 }
68
69 // 2. Find which leptons survive the OR and apply signal selection
70 for (const auto& jet : (lightjets + bjets)) {
71 ifilter_discard(leptons, [&](const DressedLepton& lep) {
72 return lep.pT() < 28*GeV || deltaR(jet, lep) < min(0.4, 0.04+10*GeV/lep.pT());
73 });
74 }
75
76 if (leptons.size() != 2) vetoEvent;
77 std::sort(leptons.begin(), leptons.end(), cmpMomByPt);
78
79 // Z veto
80 const size_t nEl = count(leptons, [](const DressedLepton& lep) { return lep.abspid() == PID::ELECTRON; });
81 const double mll = (leptons[0].mom() + leptons[1].mom()).mass();
82 if (nEl != 1 && !(fabs(mll - 91*GeV) > 15*GeV && mll > 10*GeV)) vetoEvent;
83
84 const double m00 = (leptons[0].mom() + bjets[0].mom()).mass();
85 const double m10 = (leptons[1].mom() + bjets[0].mom()).mass();
86 const double m01 = (leptons[0].mom() + bjets[1].mom()).mass();
87 const double m11 = (leptons[1].mom() + bjets[1].mom()).mass();
88 double minimax = min( max(m00,m11), max(m10,m01) );
89 minimax = min(minimax, 419.); // put overflow in the last bin
90 _h->fill(minimax/GeV);
91 }
92
93
94 /// Finalise
95 void finalize() {
96 normalize(_h);
97 }
98
99
100 private:
101
102 /// Histogram
103 Histo1DPtr _h;
104
105 };
106
107
108 RIVET_DECLARE_PLUGIN(ATLAS_2018_I1677498);
109
110}
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