V+JETS IN ATLAS. Ellie Dobson (CERN) On behalf of the ATLAS Collaboration

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1 V+JES IN ALAS Ellie Dobson (CERN) On behalf of the ALAS Collaboration

2 5 b Data taking Full 0 dataset (eriods A-I) Preselection All relevant subdetectors in stable oeration Event cleaning At least one good rimary vertex Single electron or muon trigger WZ candidate hunting Inclusive cross sections Ratios: W/Z, W+/W- Differential cross sections Boson + cross sections Boson + candidate hunting heory model testing (low x) Background to BSM hysics PDF constraints Calibration and alignment Lumi measurement 0µb nb nb 00nb b b 0b fb and beyond.

3 What we are measuring Answer: cross sections*! Quantity σ(v+ N ) BR(V) σ(v+ N ) / σ(v+ N ) dσ/dp N dσ/dh Motivation est of higher order calculations and QCD Choice of -arton matching and arton showering Constraining α s and PDFs Many uncertainties cancel out in the ratio Background to to (extraolate to higher multilicity) est of higher order calculations and QCD Understand background to new hysics H=P l +ME+ΣP - scale used in MCFM and BLACKHA-SHERPA Different roduction mechanism and energy regime to evatron Plus comarison to ALPGEN, SHERPA, PYHIA, MCFM, BLACKHA+SHERPA *within defined hase sace for η l, P l, M Z, M W, ME

4 * Just for signal samles MC Datasets and settings* Generator v. Interfaced with Comments ALPGEN. HERWIG 6.5 JIMMY 4. PHOOS.5.4 CEQ6L ALAS MC09 tune SHERPA.. CEQ6L Default UE tune PYHIA 6.4. PHOOS.5.4 MRS 007 LO ALAS MC09 tune MLM matching CKKW matching LO ME with corrections to ISR PS emission Normalised to FEWZ NNLO QCD rediction (MRS007LO PDFs) MCFM CEQ6.6/CEQ6L NLO for <=, LO for SHERPA +BLACKHA CEQ6.6M NLO for <= + Pythia UE and fragmentation corrections + recombination of FSR hotons

5 Event selection Comare with 0000 Z+ events currently analysed at the evatron Electrons P > 0 GeV η >.47 η <.7 >.5 Identification criteria Removal in bad calorimeter regions Isolation Jets AntiKt4 P > 0(0) GeV in W (Z) y (η in W analysis) <.8 ΔR (leton-) >0.5 Pileu removal cuts Muons P > 0 GeV η >.4 Quality requirements Isolation # W Z No req Event Preselection ME > 5 GeV (W) M W > 40 GeV (W) Second leton veto (W) 66 GeV < M Z < 6 GeV (Z) Oosite sign letons (Z) # W Z No req

6 QCD background estimation techniques Wlnu Zll e Fit data ME distribution - QCD and letonic temlate Loosen electron ID criteria - scale to data QCD temlate obtained by ) Electron ID reversal ) Relace electron by hoton selection mu Fit ME and M W data distribution - QCD and letonic temlate Monte Carlo Letonic backgrounds taken from MC: Wτν, Zee, Zµµ, Zττ, to, tt, VV otal background O(%)/O(-5%) for W/Z analysis

7 QCD background estimation techniques In future hoe to lay a similar game with ttbar # of Events / 5 GeV ythia W + Data 0, We QCD W Zee tt Ldt=. b ALAS s=7 ev # of Events / 5 GeV 800 W + Data 0, Wµ ythia QCD W 600 Z µ ttµ 400 Ldt=. b ALAS s=7 ev Weν miss E [GeV] Wµν miss E [GeV]

8 Sanity checks : Z mass Presence of does not affect leton reconstruction events / 5 GeV ALAS Preliminary L dt = b Z/*+,, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( e e ) + (Algen) QCD WW,WZ,ZZ tt W( e) + + Z/*( - ) + Statistical Errors Only events / 5 GeV ALAS Preliminary L dt = b Z/* +,, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( µ + WW,ZZ,WZ t t Z/*( )+ QCD W( µ)+ - µ )+ (Algen) Statistical Errors Only Zee m e + e [GeV] - m e + e [GeV] Zµµ m µ + µ

9 Sanity checks: W transverse mass Presence of does not affect ME reconstruction Entries /.5 GeV 6000 Data 0 ( s = 7 ev) W e QCD W L dt = 6 b e + ALAS Preliminary Entries /.5 GeV L dt = b Data 0 ( W µ QCD Z µµ W s = 7 ev) + µ ALAS Preliminary Weν m [GeV] Wµν m [GeV]

10 Sanity checks: P Jet resonse consistently good over whole P range events / GeV 4 ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( e e ) + (Algen) QCD WW,WZ,ZZ tt W( e) + + Z/*( - ) + Statistical Errors Only events / GeV 5 4 ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( µ µ )+ (Algen) WW,ZZ,WZ t t Z/*( )+ QCD W( µ)+ Statistical Errors Only Zee (leading ) [GeV] (leading ) [GeV] Zµµ

11 Sanity checks: multilicity ttbar background more roblematic at higher multilicity events / bin ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( e e ) + (Algen) QCD WW,WZ,ZZ tt W( e) + + Z/*( - ) + events / bin ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( µ µ )+ (Algen) WW,ZZ,WZ t t Z/*( )+ QCD W( µ)+ Statistical Errors Only Statistical Errors Only Zee 0 4 N Zµµ 0 4 N

12 Sanity checks: multilicity Backgrounds more roblematic in W analysis Events Ldt= b We + Data 0, We QCD Wdibosons Zee Z tt single to Events s=7 ev ALAS Preliminary Ldt= b Wµ + Data 0, Wµ QCD Wdibosons Zµµ Z tt single to s=7 ev ALAS Preliminary Weν Inclusive Jet Multilicity, N Wµν Inclusive Jet Multilicity, N

13 Analysis strategy Detector level Data distributions (as already seen) Unfolding: Efficiencies, resonse, trigger, accetance Particle level (ublic results) Non QCD effects: Hadronisation, underlying event, QED FSR + hase sace Parton level BLACKHA+SHERPA+ (W analysis only) MCFM NLO for W+<= ; LO for W+4 ALPGEN, SHERPA normalised to FEWZ NNLO

14 Unfolding from detector to article level Bin by bin unfolding Simle correction factor mechanism. Systematics uncertainty : difference ALPGEN and SHERPA derived corrections Bayesian unfolding Lower MC deendence, better statistical treatment Results in large fluctuations when comuting systematics in bins with low statistics Agreement of results between the two methods and highly diagonal conditional migration matrices give us confidence in the bin by bin method

15 Systematic uncertainties: W summary Dominant uncertainty Subdominant uncertainty Subsubdominant uncertainty Leton uncertainties slightly larger in electron channel

16 Systematic uncertainties: Z summary Dominant uncertainty Uncertainty conclusions comarable to W channel Subdominant uncertainty Subsubdominant uncertainty

17 Systematic uncertainty deendence Uncertainties increase with N: due to JES and BG More or less flat wrt P systematic uncertainty ALAS Preliminary Z/ *( µ µ )+ Z/ * +,, R = 0.4 > 0 GeV otal JES,JER Muon (reco, trig resol, scale) Bkg, Unfolding, JVF systematic uncertainty ALAS Preliminary Z/ *( µ µ )+, R = 0.4 > 0 GeV otal JES,JER Muon (reco, trig resol, scale) Bkg, Unfolding, JVF [GeV] Weν Zµµ 0.7 Zµµ N

18 Systematic uncertainties on NLO redictions Uncertainty Evaluation Imact Scale Vary nominal H/ u and down by factor -9% PDF Hessian method with CEQ6.6 Comarison with MSW008 variation around nominal α s UE+Frag AMB vs JIMMY Varying AMB to increase UE by % PYHIA vs HERWIG+JIMMY -% 4-8% QED FSR ALPGEN vs SHERPA and PYHIA % article->arton level Parton level cross section

19 dσ/dn ) [b] (W + N 4 Ldt= b We + Data 0, s=7 ev ALPGEN SHERPA PYHIA BLACKHA-SHERPA MCFM ALAS Preliminary ) [b] (W + N 4 Ldt= b Wµ + Data 0, s=7 ev ALPGEN SHERPA PYHIA BLACKHA-SHERPA MCFM ALAS Preliminary heory/data Weν Inclusive Jet Multilicity, N heory/data 0 Wµν Inclusive Jet Multilicity, N

20 Zee Zµµ )+ N ) [b] - (Z/*( e + Data / MC Data / MC Data / NLO e ALAS Preliminary L dt = b, R = 0.4, > 0 GeV - Z/*( e + e ) + Data 0 ( s = 7 ev) Algen Shera Pythia MCFM.6 Data 0 ( s = 7 ev) theoretical uncertainties Data 0 / Algen Data 0 / Shera NNLO normalization N N ) [b] )+ µ + (Z/*(µ Data / NLO Data / MC Data / MC - ALAS Preliminary Z/*( µ µ )+ L dt = b Data 0 ( s = 7 ev), R = 0.4, Algen > 0 GeV Shera Pythia MCFM.8 Data 0 ( s = 7 ev) theoretical uncertainties Data 0 / Algen.8 Data 0 / Shera NNLO normalization N

21 σ(n)/σ(n) - ) )/ (W + N We + Data 0, s=7 ev ALPGEN SHERPA PYHIA BLACKHA-SHERPA MCFM Ldt= b ) ) / (W + N Wµ + Data 0, s=7 ev ALPGEN SHERPA PYHIA BLACKHA-SHERPA MCFM Ldt= b (W + N Weν ALAS Preliminary (W + N /0 / / 4/ 5/4 Inclusive Jet Multilicity Ratio 0. ALAS Preliminary 0. /0 / / 4/ 5/4 Inclusive Jet Multilicity Ratio Wµν

22 Zee Zµµ N ) )+ - e + N ) / (Z/*( e )+ - e + (Z/*( e Data / NLO Data / MC Data / MC ALAS Preliminary L dt = b, R = 0.4, > 0 GeV - Z/*( e + e ) + Data 0 ( s = 7 ev) Algen Shera Pythia MCFM.6 Data 0 ( s = 7 ev).4 theoretical uncertainties Data 0 / Algen Data 0 / Shera N / N )+ N ) µ + N )/(Z/*( µ )+ µ + (Z/*(µ Data / NLO Data / MC Data / MC ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Z/*( µ µ )+ Data 0 ( s = 7 ev) Algen Shera Pythia MCFM.6 Data 0 ( s = 7 ev) theoretical uncertainties.6 Data 0 / Algen.4 Data 0 / Shera N / N

23 dσ/dp [b/gev] d/d Ldt= b W + W +, x W +, x - W + 4, x - We + Data 0, s=7 ev ALPGEN SHERPA BLACKHA-SHERPA MCFM ALAS Preliminary [b/gev] d/d Ldt= b W + W +, x W +, x - W + 4, x - Wµ + Data 0, s=7 ev ALPGEN SHERPA BLACKHA-SHERPA MCFM ALAS Preliminary heory/data heory/data Weν W + W First Jet [GeV] heory/data heory/data Wµν W + W First Jet [GeV]

24 Zee Zµµ 0 ) [/GeV] )+ - e + / (Z/*( e - - ALAS Preliminary L dt = b, R = 0.4, > 0 GeV - Z/*( e + e ) + Data 0 ( s = 7 ev) Algen Shera MCFM µ - )+ 0) [/GeV] + /(Z/*(µ - ALAS Preliminary L dt = b Z/* +,, R = 0.4, > 0 GeV Z/*( µ µ )+ Data 0 ( s = 7 ev) Algen Shera MCFM d/d d/d - Data / NLO Data / MC Data / MC.6 Data 0 ( s = 7 ev).4 theoretical uncertainties Data 0 / Algen Data 0 / Shera (leading ) [GeV] Data / NLO Data / MC Data / MC.8 Data 0 ( s Data 0 / Algen.6 Data 0 / Shera = 7 ev) theoretical uncertainties [GeV]

25 dσ/dp [b/gev] d/d Ldt= b W + W +, x We + Data 0, s=7 ev ALPGEN SHERPA BLACKHA-SHERPA MCFM ALAS Preliminary [b/gev] d/d Ldt= b W + W +, x Wµ + Data 0, s=7 ev ALPGEN SHERPA BLACKHA-SHERPA MCFM ALAS Preliminary - W + 4, x - - W + 4, x heory/data.5 W heory/data.5 W Weν Second Jet [GeV] Wµν Second Jet [GeV]

26 Zee Zµµ )+ 0 ) [/GeV] - e + / (Z/*( e - - ALAS Preliminary L dt = b, R = 0.4, > 0 GeV - Z/*( e + e ) + Data 0 ( s = 7 ev) Algen Shera MCFM µ - )+ 0) [/GeV] + /(Z/*(µ - L dt = b Data 0 ( s = 7 ev) - ALAS Preliminary, R = 0.4, > 0 GeV Z/*( µ µ )+ Algen Shera MCFM d/d -4 d/d -4 Data / NLO Data / MC Data / MC.8 Data 0 ( s = 7 ev).6 theoretical uncertainties Data 0 / Algen.6 Data 0 / Shera (nd leading ) [GeV] Data / NLO Data / MC Data / MC.8 Data 0 ( s Data 0 / Algen.6 Data 0 / Shera = 7 ev) theoretical uncertainties (nd leading ) [GeV]

27 dσ/dh ME l [b/gev] d/dh Ldt= b W + W +, x We + Data 0, s=7 ev ALPGEN SHERPA BLACKHA-SHERPA ALAS Preliminary [b/gev] d/dh Ldt= b W + W +, x Wµ + Data 0, s=7 ev ALPGEN SHERPA BLACKHA-SHERPA ALAS Preliminary - W +, x - - W +, x W + 4, x - -4 W + 4, x heory/data W + heory/data W + heory/data W [GeV] H heory/data W [GeV] H

28 Systematics: how can we do better We are already dominated by systematic and not statistical uncertainty.and no longer can hide behind the luminosity systematic (<4%) energy scale ileu unfolding background estimation new NLO redictions

29 Conclusions Detailed study at W+ and Z+ associated roduction Inclusive and differential cross sections Ratios of cross sections First comarison with W+ at NLO (Blackhat + Shera) Data unfolded to article level agrees well with NLO and LO ME+PS redictions from MCFM, Algen, and Shera Pythia is not exected to be accurate for events with more than one by construction Accuracy of the measurement is already systematically limited by uncertainties on energy scale

30 Backu

31 Background samles to W

32 MC datasets

33 Detector level sanity checks Jet resonse: seudoraidity entries / ALAS Preliminary L dt = b Z/*+,, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( e e ) + (Algen) QCD WW,WZ,ZZ tt W( e) + + Z/*( - ) + Statistical Errors Only Entries / ALAS Preliminary L dt = b Z/ * +,, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( µ µ )+ (Algen) WW,ZZ,WZ t t Z/*( )+ QCD W( µ)+ Statistical Errors Only Zee - 0 Zµµ - 0

34 Detector level sanity checks Secondary t events / GeV ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Data 0 ( s = 7 ev) Z/*( e e ) + (Algen) QCD WW,WZ,ZZ tt W( e) + + Z/*( - ) + Statistical Errors Only events / GeV 4 ALAS Preliminary L dt = b, R = 0.4, > 0 GeV Data 0 ( s = 7eV) Z/*( µ µ )+ (Algen) WW,ZZ,WZ t t Z/*( )+ QCD W( µ)+ Statistical Errors Only Zee (nd leading ) [GeV] (nd leading ) [GeV] Zµµ