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Searches for WZ and ZZ Diboson Production in Final States with Jets and Charged Leptons Or Missing Transverse Energy at CDF

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Searches for WZ and ZZ Diboson Production in Final States with Jets and Charged Leptons Or Missing Transverse Energy at CDF Searches for WZ and ZZ Diboson Production in Final States with Jets and Charged Leptons or Missing Transverse Energy at CDF Wesley Ketchum (University of Chicago) on behalf of the CDF Collaboration 19th Particle and Nuclei International Conference 7/25/2011 Motivation ν, l− @ @ q¯ ν, l • Semi-hadronic diboson @I Z − @ q¯ @ 6 + decays important step @ @@ ν¯, l @ @ + Z to Higgs @ ν¯, l @I @ Z @ ∗ – Share similar final state 6 q @@ 2 @@ for m < 135 GeV/c H ¯ H @@ b – Testing ground for new q ? @ b tools q Z @ I@ • Previous observations @ q¯ all involve WW ZZ Producon ZH Producon – Larger σ Process Cross Section (pb) WW 11.70 0.7 – Large Wl,ν branching ± ratio WZ 3.60 0.3 ZZ 1.49 ± 0.2 • In this talk ± – WZ/ZZ lν,νν + qq : MET (Missing transverse energy) + jets • b tagging to separate from WW – ZW/ZZ l+l- + qq/qqʼ : Charged leptons + jets • New quark-gluon discriminant to combat large Z + (gluon) jets background 1 7/25/11 PANIC11 2 1 Previous Tevatron WZ/ZZ Measurements Process SM σ (pb) Decay Channel σ (pb) ∫L (Year Pub.) Exp. + ‐ +1.07 ‐1 WZ 3.6 lν, l l 3.89 ‐0.90 4.1 (2010) D0 +0.8 ‐1 3.9 ‐0.7 7.1 (2011) CDF + ‐ + ‐ +0.49 ‐1 ZZ 1.5 l l , l l 1.26 ‐0.40 6.4 (2011) D0 2.18 ± 0.49 6.1 ‐1 (2011) CDF l+l‐, νν 2.01 ± 0.97 2.7 ‐1 (2008) D0 +0.60 ‐1 1.45 ‐0.51 5.9 (2010) CDF WZ 3.6 lν,jj & l+l‐,jj ? ZZ 1.5 νν,jj & l+l‐,jj ? 7/25/11 PANIC11 3 Other New Tevatron Measurements Process Experiment URL Wγ D0 hp://www‐d0.fnal.gov/Run2Physics/WWW/results/prelim/ EW/E36/ Zγ CDF hp://www‐cdf.fnal.gov/physics/ewk/2011/zgamma/ Zgamma5inv/index.html W + jj D0 hp://www‐d0.fnal.gov/Run2Physics/WWW/results/final/ HIGGS/H11B/ CDF hp://www‐cdf.fnal.gov/physics/ewk/2011/wjj/7_3.html WW/WZ CDF hp://www‐cdf.fnal.gov/physics/new/hdg/Results_files/ lν + h.f. results/wzlnubb_071911/ 7/25/11 PANIC11 4 About the Tevatron and CDF • Fermilab Tevatron – Collide p-pbar at √s = 1.96 TeV – 11.6 fb-1 delivered to experiments • Collider Detector at Fermilab (CDF) – Silicon detectors and “outer” drift chamber for particle tracking – Electromagnetic and hadronic calorimeters – Muon systems outside calorimeters 7/25/11 PANIC11 5 Event Selection MET + Jets e+e-,μ+μ- + Jets • Data from MET triggers • Data from high-pT lepton – MET > 50 GeV triggers – Quality cuts to reduce – Leptonsʼ pT > 20 GeV/c “fake” MET from multijet – 76 GeV/c2 < Dilepton Mass production < 106 GeV/c2 – Determine trigger efficiency – Determine trigger efficiency from Zμ+μ- sample by comparing data and MC in Z + 1 jet sample • Two (or more) jets – Jetsʼ ET > 20 GeV, |η| < 2.0 – Fit to Dijet Mass to extract Diboson signal 7/25/11 PANIC11 6 Artificial Neural-Network Based Jet bness Tagger • Multivariate algorithm to separate b jets from non-b jets – Long B hadron lifetimes – Large B hadron mass compared to decay products • Focus on properties of individual tracks – Train NN to assign “track bness” to each track in a jet • Consider d0, z0, pT, rapidity and pT w.r.t. jet axis (p⊥) – Combine with jet-level information to assign overall “jet bness” • Decay length in xy-plane (Lxy), existence of KS or μʼs in jet Track bness NN Jet bness Jet bness NN Value Tracks Inside Jet Jet‐Level Info 7/25/11 PANIC11 7 Jet bness Tagger /01$23&$44$56"7898&:6; *+., !"#$!"%&'( • Train using ZZ Pythia MC *+. !"%&'( :6<8#6:6;$3&8#' – Jets from Zbb decays for *+-, b jet samples *+- *+), – Jets from Zqq (no bʼs *+) present) for non-b samples *+*, * () (*+, * *+, ) !"#$%&"'' • “Tag”: Place cut on minimum CDF Run II Preliminary, !L = 4.8 fb-1 Data ! bness value for jets 400 tt Selection W Z/ZZ W+W- tt - – Optimize cut location Z" l+l +bb - 300 Z" l+l W! ! +bb – Calculate efficiency of cut in " # $# ! ! W " " $"+bb ! ! W " e $e+bb data from b-rich tt selection Events / 0.05 units W! ! 200 " # $# ! ! W " " $" – Get mistag rate from Z or W W!" e!$ + jets samples e 100 – Correct MC efficiency/mistag rate to match data 0 -1 -0.5 0 0.5 1 Highest jet bness 7/25/11 PANIC11 8 Artificial Neural-Network Based Jet Quark-Gluon Discriminant • WZ/ZZ signal is entirely quark jets – W/Z + jets background has significant gluon contribution • Gluon jets more spatially spread than quark jets – Gluons have more color Quark Gluon charge than quarks • Construct distribution of distances between pairs of towers and tracks in a jet – ΔR = [ (Δη)2 + (Δφ)2 ]½ – Weight towers/tracks by their energy/momentum content A wedge of the CDF central calorimeter. Towers’ size ~ 0.1 in η and 15° in φ. 7/25/11 PANIC11 9 Jet QG Discriminant • Content in bins of ΔR are inputs into NN discriminant – Separate NNs for tower and track distributions Distribution of Towers in Jets Distribution of Tracks in Jets 0.4 CDF Run II Preliminary 0.06 CDF Run II Preliminary Z"!+!- + 2 parton Alpgen MC Z"!+!- + 2 parton Alpgen MC Light Quark Jets Light Quark Jets 0.3 Gluon Jets Gluon Jets Energy Content 0.04 0.2 Momentum Content 0.02 0.1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.2 0.4 0.6 0.8 1 1.2 1.4 ! R Between Tower Pairs ! R Between Track Pairs Tower Neural Network Output Track Neural Network Output CDF Run II Preliminary CDF Run II Preliminary Z!!+!- + 2 parton Alpgen MC 0.06 Z!!+!- + 2 parton Alpgen MC 0.06 Light Quark Jets Light Quark Jets Gluon Jets Gluon Jets 0.04 0.04 Events (Normalized) Events (Normalized) 0.02 0.02 0 0 -1.5 -1 -0.5 0 0.5 1 1.5 -1.5 -1 -0.5 0 0.5 1 1.5 NN Output NN Output 7/25/11 PANIC11 10 Jet QG Discriminant Final QG Neural Network Output • Use third neural network to combine tower and track information, and CDF Run II Preliminary Z!!+!- + 2 parton Alpgen MC other relevant jet variables 0.06 Light Quark Jets Gluon Jets – Tower and Track NN values 0.04 – Ratios of Energy and Momentum in Events (Normalized) Cone 0.4 to 0.7 around jet 0.02 – Jet EM Fraction – Number of Tracks and Towers in jet 0 -1.5 -1 -0.5 0 0.5 1 1.5 – Jet ET, η Final QG Value • Gluon distribution normalized to match quarks tt Lepton + Jets Selection: Sum Jet QG – Number of interaction vertices CDF Run II Preliminary !L = 6.6 fb-1 • Calibrate MC response by 80 Data Events / bin Diboson comparing data and MC in W + 1 60 tt Z + b jets jet selection region 40 Z + jets W + b jets • Determine efficiency of cut on QG W + jets 20 value 0 -1 -0.5 0 0.5 1 – tt Wb, Wb lνb, qqʼb for quark-jet Sum Jet QG signal More Quark‐Like – W + jets for background-like regions 7/25/11 PANIC11 11 Backgrounds To Diboson Searches: W/Z + Jets • Dominant background for both analyses • Two different approaches MET + Jets: Charged Leptons + Jets: Photon + 2 jet data used Use MC, but scale JES of to correct MC modeling of gluon jets down based on dijet mass Z + 1 jet balancing studies CDF Run II Preliminary, <L> = 6.0 fb-1 Z-Jet Balancing: Jet QG Value 0.2 T 0.18 No-Tag Electroweak MC Template CDF Run II Preliminary, "L = 6.6 fb-1 0.16 / Z P 1.1 Data - Fakes No-Tag !+Jets Data Template T MC, JES 0 0.14 MC, JES -2! (Gluons) 1/N dN/(8 GeV) Jet E 1.05 MC, JES -1! (All) 0.12 0.1 1 0.08 0.06 0.95 0.04 0.9 0.02 -1 -0.5 0 0.5 1 0 40 60 80 100 120 140 160 2 Jet QG Value Mjj (GeV/c ) 7/25/11 PANIC11 More Quark‐Like 12 Backgrounds To Diboson Searches: Jets Faking Charged Leptons/Neutrinos • MET + Jets: MET METTrk MET – Multijet production with mismeasured jet energies can fake MET METTrk – To model… • Construct missing PT from tracks (METTrk) MET and • Δφ(MET,METTrk) > 1 MET and MET “QCD-Enhanced” Trk METTrk Aligned Not Aligned region Real MET Fake MET (from ν) • Lepton + Jets – W + 1 jet faking a lepton may pass dilepton cuts • Use like-sign objects to model muon fakes • Calculate probability of jet to fake electron from jet triggered data 7/25/11 PANIC11 13 3 -1 -1 !10 No-tag Channel / CDF Run II Preliminary, <L> = 5.5 fb 2-tag Channel / CDF Run II Preliminary, <L> = 5.5 fb 40 QCD QCD 160 35 WW WW Single Top 140 Single Top 30 tt 120 tt 25 EWK 100 EWK Events / 8 GeV Data Events / 8 GeV Data 20 80 15 60 10 40 5 20 0 0 40 60 80 100 120 140 160 40 60 80 100 120 140 160 M [GeV] M [GeV] jj MET + Jets Resultsjj 3 -1 -1 2 !10 No-tag Channel / CDF Run II Preliminary, <L> = 5.5 fb 2-tag Channel / CDF Run II Preliminary, <L> = 5.5 fb • 40 Perform χ fit to WZ+ZZ 180 WZ+ZZ QCD QCD 35 160 WW WW dijet mass in two 30 Single Top 140 Single Top 25 tt 120 tt EWK 100 EWK Events / 8 GeV Events / 8 GeV channels 20 Data Data 80 15 60 – Heavy-flavor 10 40 5 20 enriched “2-tag” 0 0 40 60 80 100 120 140 160 40 60 80 100 120 140 160 Mjj [GeV] Mjj [GeV] region 1 CDF Run II Preliminary, L =5.5 fb− No-tag Channel / CDF Run II Preliminary, <L>=5.5 fb-1 2-tag Channel / CDF Run II Preliminary, <L>=5.5 fb-1 – Remaining events in 500 Process(es) Fit Nevents (no-tag) Fit Nevents (2-tag) WZ+ZZ ! WZ+ZZ 400 “no-tag” region Standard Model 20 Standard Model 300 EWK 153300 3000 694 48 Data - BGs±+34 ±+13 Data - BGs 200 ¯ 10 tt 517 36 129 15 • Best fit: N ~ Events / 8 GeV 100 − Events / 8 GeV +24− WZ/ZZ 0 single t 1180 130 0 183 26 ± − SM prediction -100 QCD 72300 2800 -10 54.6 7.3 -200 ± ±+1.8 -300 WW 2720 190 8.3 -20 1.9 • Use Feldman- 40 60 80 100 120 140± 160 40 60 − 80 100 120 140 160 WZ/ZZ 1160M [GeV]620 39.9 20 M [GeV] jj± ± jj Cousins method to 1 CDF Run II Preliminary, L =5.5 fb− extract sensitivity Process(es) Fit Nevents (no-tag) Fit N!events (2-tag) EWK 153300 3000 694 48 ± ± ¯ +24 tt and single t 1700 140 313 26 +3.6 ± − σ = 5.0 pb QCD 72300 2800 54.6 7.3 WZ/ZZ ‐2.5 ± ±+1.8 WW 2720 190 8.3 1.9 < 13 pb at 95% CL ± − WZ/ZZ 1160 620 39.9 20 ± ± 7/25/11 PANIC11 14 Charged Leptons + Jets Results CDF Run II Preliminary, ! L = 6.6 fb-1 Heavy Flavor Tag Channel Light Flavor Tag Channel No-Tag Channel • Perform χ2 fit to dijet 2 2 600 2 100 WZ+ZZ WZ+ZZ 800 WZ+ZZ Z+jets
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