Rivet analyses referenceATLAS_2020_I1788444Differential cross-sections for Z + b-jetsExperiment: ATLAS (LHC) Inspire ID: 1788444 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
This paper presents a measurement of the production cross-section of a $Z$ boson in association with $b$-jets, in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 35.6 fb$^{-1}$. Inclusive and differential cross-sections are measured for events containing a $Z$ boson decaying into electrons or muons and produced in association with at least one or at least two $b$-jets with transverse momentum $p_T> 20$ GeV and rapidity $|y|<2.5$. Predictions from several Monte Carlo generators based on leading-order (LO) or next-to-leading-order (NLO) matrix elements interfaced with a parton-shower simulation and testing different flavour schemes for the choice of initial-state partons are compared with measured cross-sections. The 5-flavour number scheme predictions at NLO accuracy agree better with data than 4-flavour number scheme ones. The 4-flavour number scheme predictions underestimate data in events with at least one $b$-jet. N.B.: Data correspond to average of electron and muon channel. Use LMODE=EL,MU to run on individual channels. Source code: ATLAS_2020_I1788444.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/ZFinder.hh"
4#include "Rivet/Projections/FastJets.hh"
5#include "Rivet/Projections/VetoedFinalState.hh"
6#include "Rivet/Projections/HeavyHadrons.hh"
7#include "Rivet/Projections/PromptFinalState.hh"
8
9namespace Rivet {
10
11 /// @brief Z + b(b) in pp at 13 TeV
12 class ATLAS_2020_I1788444 : public Analysis {
13 public:
14 /// @name Constructors etc.
15 //@{
16 /// Constructor
17 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2020_I1788444);
18 //@}
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22
23 _mode = 0;
24 if ( getOption("LMODE") == "EL" ) _mode = 1;
25 if ( getOption("LMODE") == "MU" ) _mode = 2;
26
27 const FinalState fs;
28 // Define fiducial cuts for the leptons in the ZFinder
29 Cut lepcuts = (Cuts::pT > 27*GeV) & (Cuts::abseta < 2.5);
30 ZFinder zfinderE(fs, lepcuts, PID::ELECTRON, 76*GeV, 106*GeV);
31 ZFinder zfinderM(fs, lepcuts, PID::MUON, 76*GeV, 106*GeV);
32 declare(zfinderE, "zfinderE");
33 declare(zfinderM, "zfinderM");
34
35 declare(HeavyHadrons(), "HFHadrons");
36
37 // // Photons
38 FinalState photons(Cuts::abspid == PID::PHOTON);
39 // Muons
40 PromptFinalState bare_mu(Cuts::abspid == PID::MUON, true);
41 DressedLeptons all_dressed_mu(photons, bare_mu, 0.1, Cuts::abseta < 2.5, true);
42 // Electrons
43 PromptFinalState bare_el(Cuts::abspid == PID::ELECTRON, true);
44 DressedLeptons all_dressed_el(photons, bare_el, 0.1, Cuts::abseta < 2.5, true);
45
46 //Jet forming
47 VetoedFinalState vfs(FinalState(Cuts::abseta < 4.5));
48 vfs.addVetoOnThisFinalState(all_dressed_el);
49 vfs.addVetoOnThisFinalState(all_dressed_mu);
50
51 FastJets jets(vfs, FastJets::ANTIKT, 0.4, JetAlg::Muons::ALL, JetAlg::Invisibles::DECAY);
52 declare(jets, "jets");
53
54 // book histos - binning taken from data.yoda
55 book(_h["i1b_ZpT"],2,1,1);
56 book(_h["i1b_ZY"],4,1,1);
57 book(_h["i1b_dPhiZb"],6,1,1);
58 book(_h["i1b_dRZb"],8,1,1);
59 book(_h["i1b_dYZb"],7,1,1);
60 book(_h["i1b_bpT"],3,1,1);
61 book(_h["i1b_bY"],5,1,1);
62
63 book(_h["i2b_ZpT"],13,1,1);
64 book(_h["i2b_dPhibb"],9,1,1);
65 book(_h["i2b_dRbb"],11,1,1);
66 book(_h["i2b_dYbb"],10,1,1);
67 book(_h["i2b_Mbb"],12,1,1);
68 book(_h["i2b_pTbb"],14,1,1);
69 book(_h["i2b_pTOnMbb"],15,1,1);
70
71 book(_h["ib_nBJets"],1,1,1);
72 }
73
74 /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
75 /// Perform the per-event analysis
76 void analyze(const Event& event) {
77
78 const ZFinder& zfinderE = apply<ZFinder>(event, "zfinderE");
79 const Particles& els = zfinderE.constituents();
80 const ZFinder& zfinderM = apply<ZFinder>(event, "zfinderM");
81 const Particles& mus = zfinderM.constituents();
82
83 // default is to run average of Z->ee and Z->mm
84 // use LMODE option to pick one channel
85 if ( (els.size() + mus.size()) != 2 ) vetoEvent;
86
87 if ( _mode == 0 && !(els.size()==2 || mus.size()==2) ) vetoEvent;
88 else if ( _mode == 1 && !(els.size() == 2 && mus.empty()) ) vetoEvent;
89 else if ( _mode == 2 && !(els.empty() && mus.size() == 2) ) vetoEvent;
90
91 double Vpt = 0, Vy = 0, Veta = 0, Vphi = 0;
92
93 if ( els.size()==2 ) {
94 Vpt = zfinderE.boson().pt()/GeV;
95 Vphi = zfinderE.boson().phi();
96 Vy = zfinderE.boson().rapidity();
97 Veta = zfinderE.boson().eta();
98 } else {
99 Vpt = zfinderM.boson().pt()/GeV;
100 Vphi = zfinderM.boson().phi();
101 Vy = zfinderM.boson().rapidity();
102 Veta = zfinderM.boson().eta();
103 }
104
105 Jets jets = apply<JetAlg>(event, "jets").jetsByPt(Cuts::pT>20*GeV && Cuts::absrap < 2.5);
106 idiscardIfAnyDeltaRLess(jets, els, 0.4);
107 idiscardIfAnyDeltaRLess(jets, mus, 0.4);
108
109 Jets btagged;
110 const Particles allBs = apply<HeavyHadrons>(event, "HFHadrons").bHadrons(5.0*GeV);
111 Particles matchedBs;
112
113 for (const Jet& j : jets) {
114 Jet closest_j;
115 Particle closest_b;
116 double minDR_j_b = 10;
117
118 for (const Particle& bHad : allBs) {
119 bool alreadyMatched = false;
120 for (const Particle& bMatched : matchedBs) {
121 alreadyMatched |= bMatched.isSame(bHad);
122 }
123 if(alreadyMatched) continue;
124
125 double DR_j_b = deltaR(j, bHad);
126 if ( DR_j_b <= 0.3 && DR_j_b < minDR_j_b) {
127 minDR_j_b = DR_j_b;
128 closest_j = j;
129 closest_b = bHad;
130 }
131 }
132
133 if(minDR_j_b < 0.3) {
134 btagged += closest_j;
135 matchedBs += closest_b;
136 }
137 }
138 //size_t njets = jets.size();
139 size_t ntags = btagged.size();
140 if (ntags < 1) vetoEvent;
141
142 _h["ib_nBJets"]->fill(1); //inclusive 1-b
143
144 double dYVb = fabs(Vy - btagged[0].rap());
145 double dEtaVb = fabs(Veta - btagged[0].eta());
146 double dPhiVb = deltaPhi(Vphi, btagged[0]);
147 double dRVb = sqrt(dEtaVb*dEtaVb + dPhiVb*dPhiVb);
148
149 _h["i1b_ZpT"] ->fill(Vpt/GeV);
150 _h["i1b_ZY"] ->fill(fabs(Vy));
151 _h["i1b_dPhiZb"]->fill(dPhiVb);
152 _h["i1b_dRZb"]->fill(dRVb);
153 _h["i1b_dYZb"]->fill(dYVb);
154 _h["i1b_bpT"]->fill(btagged[0].pt()/GeV);
155 _h["i1b_bY"]->fill(btagged[0].absrap());
156
157 if ( ntags>1 ) {
158 _h["ib_nBJets"]->fill(2); //inclusive 2-b
159
160 double dYbb = fabs(btagged[0].rap() - btagged[1].rap());
161 double dPhibb = deltaPhi(btagged[0], btagged[1]);
162 double dRbb = deltaR(btagged[0], btagged[1]);
163 double Mbb = (btagged[0].mom() + btagged[1].mom()).mass()/GeV;
164 double Ptbb = (btagged[0].mom() + btagged[1].mom()).pt()/GeV;
165
166 _h["i2b_ZpT"]->fill(Vpt);
167 _h["i2b_dPhibb"]->fill(dPhibb);
168 _h["i2b_dRbb"]->fill(dRbb);
169 _h["i2b_dYbb"]->fill(dYbb);
170 _h["i2b_Mbb"]->fill(Mbb);
171 _h["i2b_pTbb"]->fill(Ptbb);
172 _h["i2b_pTOnMbb"]->fill(Ptbb/Mbb);
173
174 }
175 }
176
177
178 void finalize() {
179 // routine accepts both Z->ee and Z->mm
180 // data corresponds to average
181 const double sf = _mode? 1.0 : 0.5;
182 scale(_h, sf * crossSectionPerEvent());
183 }
184
185 protected:
186
187 size_t _mode;
188
189 private:
190
191 map<string, Histo1DPtr> _h;
192
193 };
194
195 RIVET_DECLARE_PLUGIN(ATLAS_2020_I1788444);
196}
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