tt + production cross-section measurement at s=13TeV in the - PowerPoint PPT Presentation

tt ̅ + 𝜹 production cross-section measurement at √ s=13TeV in the semileptonic channel USLUA meeting, October, 2018 Titas Roy Florida Institute of Technology 1

Introduction and Motivation The top quark being the heaviest quark, the way it interacts with a gauge boson makes an • interesting study and can be a window for new physics. This measurement can also be used for: • 2 ∝ σ tt ̅γ a direct measurement of top quark charge : q t • top quark electroweak coupling as q t and anomalous magnetic moment can be studied • through this process. tt ̅ charge assymetry by selecting tt ̅ + γ events. • tt ̅ + γ : important background in many BSM searches and in Higgs analyses. • γ b q ¯ b g jsf q q ffknf q 0 ¯ t q 0 ¯ bfjb W + t W + ¯ t ¯ ¯ t b ¯ b W � bfbf W � ¯ jbfbf ν ¯ ` ν q ` g ` � γ ` � fbb 2

Event and Object Selection • Top quark pair selection : -1 3 Prefit 35.8 fb (13 TeV) 10 × Events Data Z+jets • Lepton Selection : exactly 1 high P T , CMS t t + W+ γ γ 1 t t Z+ γ Preliminary Work in Progress t+ γ WW/WZ/ZZ isolated lepton e+jets, N 4, N 1 Single top ttV ≥ ≥ 0.8 b j W+jets Multijet Uncertainty • Muon P T > 30 GeV, Ele P T > 35 GeV 0.6 • >=4 jets (P T > 30 GeV), at least one 0.4 btagged 0.2 • Photon Selection : 1.5 Data/MC 1 • >=1 isolated photon in barrel, P T > 20 0.5 20 40 60 80 100 120 140 Photon Et (GeV) Photon E T (GeV) GeV -1 3 Prefit 35.8 fb (13 TeV) 10 × 1.2 Events Data Z+jets -1 3 Prefit 35.8 fb (13 TeV) CMS 10 × t t + γ W+ γ Events t t Z+ γ Data Z+jets Preliminary Work in Progress 1 CMS 3 t+ γ WW/WZ/ZZ t t + W+ γ γ e+jets, N 4, N 1 Single top ttV t t Z+ γ ≥ ≥ Preliminary Work in Progress t+ WW/WZ/ZZ b γ j W+jets Multijet 2.5 0.8 e+jets, N ≥ 4, N ≥ 1 Single top ttV Uncertainty b j W+jets Multijet Uncertainty 2 0.6 1.5 0.4 1 0.2 0.5 1.5 Data/MC 1.5 Data/MC 1 1 0.5 0.5 40 60 80 100 120 140 160 180 200 4 5 6 7 8 9 10 3 Electron p (GeV) N Jets T

Analysis Strategy We want to distinguish tt ̅ + 𝜹 from background Top and Non-top samples can be distinguished with M3 variable Non-Top W 힬 , Other Bkg Z 힬 M3 - the invariant mass of the three jets with the highest M3 m top summed pT, expected to reconstruct the top quark mass. tt 힬 Top tt -1 35.8 fb (13 TeV) 〉 Data Events / GeV 35 CMS t t + Isolated t t + Nonprompt γ γ M3 m top t t Isolated t t Nonprompt Work in Progress Preliminary 30 V+ γ Isolated V+ γ Nonprompt Genuine 힬 Fake 힬 e+jets Isolated Other Isolated Other Nonprompt Uncertainty 25 Prefit Genuine and fake 힬 20 can be distinguished 〈 with Ch. Iso variable 15 ChIso ChIso 10 -1 35.8 fb (13 TeV) 5 〉 Data Events / GeV CMS t t + γ Isolated t t + γ Nonprompt 0 t t Isolated t t Nonprompt 1.5 Preliminary Data/MC Work in Progress V+ γ Isolated V+ γ Nonprompt 1 e+jets Other Isolated Other Nonprompt 4 Uncertainty 10 0.5 Prefit 100 150 200 250 300 350 400 450 500 M3 (GeV) 〈 3 10 Charged Hadron Isolation - sum of the transverse momentum of all charged hadrons in a cone centred around a photon. 1.5 Data/MC 1 0.5 0 2 4 6 8 10 12 14 16 18 20 4 Photon Ch. Had. Isolation (GeV)

Photon Categories Through generator matching we divide our photons into 4 categories based on where it is radiated from. Genuine : if the photon has a leptonic, bosonic or quark parents • Photon is actually a Misidentified electron • Hadronic Photon : radiated from a hadronic source, example: pion • Hadronic Fake : when the reconstructed photon cannot be matched to a generator level • photon. -1 3 35.8 fb (13 TeV) 10 × Events 4.5 Data t t + γ CMS t t t+ γ Isolated (signal) photons: Genuine 4 Preliminary Work in Progress Single top W+jets e+jets, N 4, N 1 Z+jets W+ ≥ ≥ γ photons and Misidentified electrons 3.5 b j Z+ WW/WZ/ZZ γ ttV Multijet 3 NonPrompt (background) photons: 2.5 Hadronic photons & hadronic fakes: 2 1.5 1 All MC samples are divided into 0.5 Isolated and NonPrompt templates Genuine Mis-id ele Hadronic Photon Hadronic Fake Photon Category 5

Data based template for Hadronic/Fake photons Data based templates used to avoid any mismodeling in NonPrompt • photons We extract the shape of these background photons from the σ i η i η • sideband region of Charged Hadron Isolation which is dominated by nonprompt photons. -1 35.8 fb (13 TeV) -1 3 35.8 fb (13 TeV) 10 × Normalized events 3 Events Data σ i η i η sideband CMS CMS 0.1 Data Data sideband Work in Progress σ Preliminary η η Work in Progress Preliminary 2.5 Genuine Photons e+jets, 4j 1b ≥ ≥ MC Nonprompt photons e+jets 0.08 MisID Electrons barrel barrel 2 Hadronic Photons 0.06 Hadronic Fakes 1.5 0.04 signal region sideband region 1 0.02 0.5 0 3 − 0 2 4 6 8 10 12 14 16 18 20 10 × 0 Photon charged-hadron isolation (GeV) 0 5 10 15 20 25 Photon σ Photon σ i η i η η η 6

Control Regions in the Fit Events -1 3 -1 35.8 fb (13 TeV) 10 35.8 fb (13 TeV) × 1000 Events / GeV Events / GeV Data 4000 Data CMS CMS t t + γ t t + Isolated t t + Nonprompt γ γ t t t t Isolated t t Nonprompt Preliminary 3500 Work in Progress Preliminary Work in Progress V+ γ V+ Isolated V+ Nonprompt 800 γ γ e+jets, 0-photon Other e+jets Other Isolated Other Nonprompt 3000 Uncertainty Uncertainty 2500 600 2000 400 1500 1000 200 500 0 0 1.5 Data/MC 1.5 Data/MC 1 1 0.5 0.5 0 2 4 6 8 10 12 14 100 200 300 400 500 600 >=4jets, 0 btag CR 0-photon CR >=4jets,0btag 0-photon CR >=4jets, 0 btag >=4jets, 0 btag To get a better handle on W/Z + To get a better handle on ttbar gamma process process 7

Fit Results • Measuring the following: • Fiducial σ tt ̅ + 𝜹 : Semileptonic top decay with a photon of PT>20 GeV, in barrel • Inclusive σ tt ̅ + 𝜹 : inclusive in top decay and fiducial in photon cuts (P T >20 GeV, in barrel) • NonPrompt photon correction factor extracted from the fit. • Ratio (R) of tt ̅ + 𝜹 to tt ̅ cross-section also calculated Electron Efficiency CMS Internal CMS Internal Work in Progress Work in Progress r = 2.68 0.181 r = 2.93 0.182 ± ± 1 1 FSR 2 Luminosity 2 Luminosity 3 MisIdentified electron scaling 3 MC Statistics in Ch. Had. Iso. 4 MC Statistics in Ch. Had. Iso. 4 Muon Efficiency 5 Photon Efficiency 5 MisIdentified electron scaling 6 B-tagging 6 Photon Efficiency 7 FSR 7 PDF TTbar 8 V+gamma Normalization 8 B-tagging 9 Pileup 9 ISR 10 MC Statistics in M3 10 MC Statistics in M3 11 Jet Energy Correction 11 V+gamma Normalization 12 Jet Energy Resolution 13 MC Statistics in 0-btag Control Region 12 Jet Energy Correction 14 ISR 13 Shape of DataDriven templates 15 PDF TTbar 14 Pileup 16 Electron Energy Smearing 15 Renormalization/Factorization Scale 17 Electron Energy Scale 16 Photon Energy Smearing 18 Renormalization/Factorization Scale 17 MC Statistics in 0-btag Control Region 19 Photon Energy Scale 18 Jet Energy Resolution 20 Shape of DataDriven templates 19 Photon Energy Scale 21 Photon Energy Smearing 20 Other Bkg Normalization 22 Other Bkg Normalization 21 prop_binM3_control 23 PDF TTGamma 22 24 prop_binM3_control PDF TTGamma 2 1 0 1 2 0.05 0 0.05 2 1 0 1 2 0.05 0 0.05 − − − − − − ( - )/ ( - )/ θ θ Δ θ r θ θ Δ θ r Δ Δ Pull +1 Impact -1 Impact Pull +1 Impact -1 Impact σ σ σ σ 0 0 Fitting to extract the inclusive cross-section 8

Summary We get the following preliminary results in the lepton+jets channel: • Inclusive cross-section = 2.63 ± 0.14(syst) ± 0.07(stat)pb 
 • Ratio = (3.21 ± 0.18(syst) ± 0.06(stat)) × 10 -3 • Fiducial cross-section being finalised • Final results coming soon! • 9

Backup 10

Object Selection Trigger Electrons • Tight electron Mu: HLT_IsoMu24_v or HLT_IsoTkMu24_v • • Tight Electron ID • P T > 35 GeV, η < 2.1 • Ele: HLT_Ele32_eta2p1_WPTight_Gsf_v • Pass gap b/w barrel and endcap • Impact parameter cuts : d0< 0.05(barrel), d0< 0.1 (endcap) Muons dz<0.1(barrel), dz<0.2(endcap) • Veto Electrons: • Pass Electron Veto ID Tight muon • • P T > 15 GeV, η < 2.5 Tight Muon ID • • Pass gap b/w barrel and endcap P T > 30 GeV, η < 2.4 • • Impact parameter cuts as above RelIso < 0.15 • • Loose Muon: • Loose Muon ID P T > 15 GeV, η < 2.4 • Jets RelIso < 0.25 • P T > 30 GeV, η < 2.4 • Photon Tight JetID • Remove Jets close to a lepton if • dR(jet,lep)< 0.4 P T > 20 GeV, η < 2.5 (barrel); • Remove Jets close to a photon if • 1.4442 > η > 1.566 (endcap) dR(jet,pho)< 0.1 btagging : deep csv > 0.8484 • Cut Based Medium Photon ID • 11