Observation and measurement of HW+W-

Part 1: INTRODUCTION

Contents Introduction Analysis overview Data samples and reconstruction Event selection Signal processes Background processes Fit procedure and uncertainties Yields and distributions Results and interpretations Part 1 Part 2 Part 3 Part 4 Part 5 This is a paper of 73 pages/~90 editors!

Introduction Motivation of the work Review of current status Production channels Overview of the results Paper structure

Analysis Overview : major background

Analysis Strategy: Categorization Discriminating variables (BDT for VBF, MT for ggF)

Part 2: Detector and samples

大型强子对撞机（LHC） 位于欧洲核子研究中心（CERN） 周长27km，跨越瑞士法国国境，总投资40亿美元 日内瓦湖 Large Hadron Collider 机场 CMS ATLAS LHCb ALICE 大型强子对撞机（LHC） 位于欧洲核子研究中心（CERN） LHC time line : 1992 : expressions of interest 1995.10 : LHC TDR published 2009.11: first pp collisons at CME=900 GeV 2010.2: first pp collisions at CME=7 TeV 2011: CMS and ATLAS recorded ~5/fb of data 2012: CMS and ATLAS ~20/fb at CME=8 TeV 2015 – 2018 data-taking at CME = 13 TeV m 周长27km，跨越瑞士法国国境，总投资40亿美元 世界能量最高最大的加速器，设计质心系能量14TeV(14x1012eV) 8 8 8

Length: ~ 46 m Radius : ~ 12 m Weight : ~ 7000 tons Channels: ~ 108 Muon spectrometer air-core toroids, MDT+RPC+TGC+CSC s/pT ~ 2-7 % |h| < 2.7, |h|<2.5 ( precision phys.) Length: ~ 46 m Radius : ~ 12 m Weight : ~ 7000 tons Channels: ~ 108 Lcable: ~ 3000 km Cost: 541M CHF EM Calorimetry Pb-LAr s/E ~ 10%/√E(GeV)1% |h|<3.2, |h| < 2.5 (fine granularity) Inner detector (B=2 T) Si pixels and strips Transition Radiation Detector (e/ separation) s/pT ~ 0.05% pT(GeV)0.1%; |h| < 2.5, B=2 T(central solenoid) Hadron Calorimeter Fe/scintillator (central), Cu/W-LAr (fwd) s/E ~ 50%/√E(GeV)3% ||<3

ATLAS TDAQ

Detector and data samples Coordinate system Trigger Data: 2011, 7 TeV 4.5fb-1, 2012, 8 TeV, 20.3 fb-1 Reconstruction Vertex / Electron/ Muon /lepton isolation/ Jet / b- tagging / MET (METrel) pTMiss, pTMiss(track)

MC simulations

Part 3: Event selection

Event selection : Initial sample Initial sample: pT1>22 GeV, pT2>10 GeV, Opposite charge, no 3rd lepton(with pT>10 GeV), vertex, trigger. 𝑒𝜇 channel: 1.33*105 events, expect 800 signal events) , sqrt(1.33E+5) = 365. 𝑒𝑒/𝜇𝜇 channel: 1.6*107 events

DISCUSSION Mar 23 Why 𝑠/ 𝐵 , not 𝑠/√(𝑆+𝐵) ? (see page 14) Definition of METrel

JVF

Event selection

Distributions after preselection

Discriminating variables of nj=0

Discriminating variables for nj=1

Discriminant variable for nj=2(VBF)

nj=2, ggF

Cut-flow : nj=0

Cut flow: nj = 1

Cut-flow(nj>=2, VBF)

BDT analysis for VBF

Cut-flow nj>=2, ggF

mT : fitting variable

BDT output: fitting variable

Kinematics in Signal regions(1)

Kinematics in Signal region(2)

Event display

Are we done yet?

Part 4: Signal and Background

Signal processes Theory Cross sections at NNLO in QCD, NLO in EWK. (10% uncert) ggF: resummation to NNLL. BR(HW+W- ) =22% (4.2% relative uncertainty)

Signal processes Theory Cross sections at NNLO in QCD, NLO in EWK. (10% uncert) ggF: resummation to NNLL. BR(HW+W- ) =22% (4.2% relative uncertainty)

Background processes WW Top Mis-identified leptons (Wj + jj) Other dibosons Example: nj=0 SR 𝑀 𝑙𝑙 <55 GeV , ∆𝜑(𝑙𝑙) < 1.8 WW CR 55< 𝑀 𝑙𝑙 <110 GeV, ∆𝜑(𝑙𝑙) < 2.6

WW CR  SR (nj <= 1) nj<=1 : CR – SR 𝑀 𝑙𝑙 extrapolation Selected with 𝑒𝜇 events 𝑝 𝑇 𝑙2 >15 GeV nj=0: 𝑝 𝑇 𝑙𝑙 >30 GeV, ∆𝜑 𝑙𝑙 >2.6, 55< 𝑀 𝑙𝑙 <110 GeV nj=1: 𝑚 𝑇 𝑙 >50 GeV, 𝑀 𝑙𝑙 > 80 GeV

Systematic uncertainties WW CR  SR (nj <= 1) Systematic uncertainties nj<=1 : CR  SR 𝑀 𝑙𝑙 extrapolation

WW MC (nj>=2) nj>=2: SHERPA MC, normalized with MCFM(large top-quark contribution, CR difficult to define for WW) Validation region: MT>100 GeV, MT2>160 GeV Data/MC ratio in validation region: 1.15+-0.19

Top quarks (nj=0) nj=0: CR= preselection, 𝑒𝜇 channel, ∆𝜑(𝑙𝑙) <2.8, any nj Purity : 74% Correction to the “extrapolation factor” alpha determined with 1 b-tag CR:1.006 Total uncertainty: 8%

Top quarks (nj=1) CR: preselection, 𝑒𝜇 channel only, exactly 1 jet (b- tagged) MTl > 50 GeV Extrapolating from 1-btag to 0-btag Total uncertainty: 5%

Top quarks (VBF: nj >=2 ) CR: exactly 1 b-tag. BDT analysis, ttbar MC modeling systematics

Top quarks (ggF, njet>=2) Defined with 𝑀 𝑙𝑙 >80 GeV (70% purity) Uncertainty on the extrapolation factor < 4%

Fake lepton: W+j CR: one lepton “anti-identified”. Extrapolation factor: measured from Z+jets Background famine in “identified lepton” at high pT

Misid extrapolation factor

Multi-jet CR: two anti-identified leptons Fake factor measured with multi-jet sample, applied twice. ARE WE DOULE COUNTING multi-jet?

Other dibosons 𝑊𝛾,𝑊𝑍/ 𝛾 ∗ , 𝑍𝑍 (10% of total background, same magnitude as the signal) 𝑒𝜇 channel: same sign CR for normalization 𝑒𝑒/𝜇𝜇: MC for both normalization and shape Validation : Electron with no b-layer hit to catch 𝑊𝛾(photon conversion also studied with 𝑍→𝜇𝜇𝛾) 𝑊𝑍/ 𝛾 ∗ Validation : 𝑒𝜐𝜇𝜇, 𝑀 𝜇𝜇 < 7 GeV, pTmiss > 20 GeV

Same sign CR

𝑊𝛾,𝑊𝑍/ 𝛾 ∗ validation

Drell Yan : Z𝜏𝜏 CRs nj=0: 𝑀 𝑙𝑙 <90 GeV, ∆𝜑(𝑙𝑙) >2.8, purity:91% nj=1: 𝑀 𝑙𝑙 <80 GeV, 𝑀 𝜏𝜏 > (mZ-25 GeV) (collinear approximation), purity: 80% nj>=2 ggF: 𝑀 𝑙𝑙 <70 GeV, ∆𝜑(𝑙𝑙) >2.8 purity 74% nj>=2 VBF: 𝑀 𝑙𝑙 <80 GeV (75 for 𝑒𝑒/𝜇𝜇 ) , | 𝑀 𝜏𝜏 – mZ|<25 GeV

Drell Yan CR

DY 𝑒𝑒/𝜇𝜇 in nj<=1 Matrix method using frecoil cut : uncertainty ~ 50%

DY 𝑒𝑒/𝜇𝜇in nj>=2 VBF ABCD method using pTmiss and 𝑀 𝑙𝑙

Summary of CRs

Summary of corrections from CR Are we done yet?

Part 5: Fit and results

Fit regions : SR

Likelihood function, and LLR

Uncertainty on signal

Uncertainty on background

Post-fit uncertainties (%)

Checks of the fit (ranking plot)

Post-fit yields

Post-fit MT (nj=0/1 𝑒𝜇 )

Post-fit MT nj=0,1 𝑒𝑒/𝜇𝜇

Post-fit MT (nj>=2 ggF VBF Cross-Check)

VBF (BDT analysis)

Observation!

Signal strength

Mass and signal strength

Ratio of VBF/ggF signal strengths

Signal strengths

Uncertainties

“Exclusion plot”