Top physics at CDF Koji Nakamura on behalf of CDF collaboration "New Developments of Flavor Physics" March 9 th, 2009

Top Quark at Tevatron  What is top quark?  Evidenced in 1994 by CDF, discovered in 1995 by Tevatron  The heaviest quark so far. The Mass is about 172 GeV.  Now We have much more data to analyze top quark properties. 24 Aug, 2008 Record : 3.8 fb -1 Good Data: 3.2 fb -1

Top Quark at Tevatron  What is top quark?  Evidenced in 1994 by CDF, discovered in 1995 by Tevatron  The heaviest quark so far. The Mass is about 172 GeV.  Now We have much more data to analyze top quark properties. Mass Charge Production Cross Section Fwd-Bwd Asymmetry Production Mechanism W helicity New Physics FCNC ttbar resonance charged Higgs …… Top Quark properties in pair production

30% : 70% Top Quark at Tevatron ~ 6.7 pb ~ 2.9 pb  What is top quark?  Evidenced in 1994 by CDF, discovered in 1995 by Tevatron  The heaviest quark so far. The Mass is about 172 GeV.  Now We have much more data to analyze top quark properties. Single top production is allowed in SM

Singletop production

Both CDF and D0 Submitted to PRL CDF DØ arXiv.org: arXiv.org: Lumi : 3.2 fb-1 Expected : 5.9 σ Observed : 5.0 σ Lumi : 2.3 fb-1 Expected : 4.5 σ Observed : 5.0 σ Observation

Why Single Top Quark? Production rate is proportional to |V tb | 2  t = (1.98 ± 0.25) |V tb | 2 pb  s = (0.88 ± 0.11) |V tb | 2 pb Top Polarization study Probe Non Standard Model phenomena Single top quarks are 100% polarized in SM Can test this with angular distribution of top decay Can search for heavy W’ boson or H ± Technical Motivation Test of the methodology for Higgs search (the same final state as the WH  lνbb signal)

2 or 3 high Pt jets (Pt>20 GeV) One high Pt lepton (Pt>20 GeV) Large Missing Energy (Et>25 GeV) Event topology difficulty Singletop production with decay into lepton + 2 jets final state Singletop Top pair Signal is hidden under the huge bkg  Multivariate analyses are needed Dominant process of 4 jets bin  counting method is possible Background (at least 1 b-tag)

Analysis strategy CDF Data SetSignal ModelBackground Model Event Selection Likelihood Function Multivariate Analysis Blind analysis Split in sub set of different purity Cross section measurement Discriminant |V tb | measurement Significance and xsec limit Lepton Trigger EventMet + Jets Trigger Event Neural Network Matrix Element Boosted Decision Tree Non triggered leptonNo lepton Neural Network Multivariate Analysis Lep+jets

Likelihood Analysis Used projective likelihood function to combine the separation power of several variables. t-channel optimized analysis s-channel optimized analysis Example of input variables 2 b-tag events Only Example of input variables HTHT Q*η pTpT MlνbMlνb

Result of Likelihood Analyses t-channel optimized analysis s-channel optimized analysis Expected significance: 4.1 σ Observed significance: 2.4 σ Expected significance: 1.1 σ Observed significance: 2.0 σ s- and t-channel are the signal s-channel is the signal 2 b-tag events Only

Combination of Likelihood Analyses To obtain s- and t-channel cross section in  s -  t plane, We perform s- and t-channel cross section fit simultaneously. Combine following 2 analyses: 1-b-tag events -- optimized to t-channel 2-b-tag events -- optimized to s-channel

Matrix Element Analysis Using Matrix Element information to calculate probabilities for seven different underlying processes: s-channel, t-channel, Wbb, tt, Wcc, Wc+jet and Wgg.

Expected significance: 4.9 σ Observed significance: 4.3 σ Result of ME Analysis

The other MV Techniques Neural Network analysis Boosted Decision Tree analysis Sequence of binary splits using the discriminating variable which gives best sig-bkg separation. An orthodox NN analysis using Neuro Bayes Program variables are used

Expected significance: 5.2 σ Observed significance: 3.5 σ Result of NN and BDT analyses Neural Network analysis Boosted Decision Tree analysis

Combination : 5 lep+jets analysis Discriminant outputs from analyses (LFT, LFS, ME, NN, BDT ) are combined into a single, more powerful super discriminant (SD) using neural networks(NEAT). Expected significance: > 5.9 σ Observed significance: 4.8 σ

MET+jets without lepton channel Using no Lepton events by MET+jets Trigger. Independent sample from lepton+jets analysis. Using NN based event selection and NN based discriminant. Challenging!! Huge QCD background… Expected significance: 1.4 σ Observed significance: 2.1 σ

CDF Combination and Singletop Conclusion Finally, we combined Super Discrimant analysis and no Lepton analysis. Expected significance: > 5.9 σ Observed significance: 5.0 σ |V tb |=0.91± 0.11 (exp.) ± 0.07 (theory) Assuming no anomalous coupling |V tb |>0.71(95% CL) Cross section: |V tb | calculation:

ttbar properties L>=2.7 fb -1 result only (second half of 2008 and 2009) Top Quark Mass Measurement Top Quark production cross section W helicity Forward Backward asymmetry ttbar production mechanism Search for the FCNC top decay Search for the stop Mimicking Top Event Signatures Search for charged higgs in top decay Search for the t’ quark …… backup

 Most of analysis fit the top quark mass with in-situ JES systematic.  The uncertainty of the top mass result is already systematic dominant. 0.85% precision 10% improved  We need reconsidering systematics. e.g. New Systematic Uncertainty Color Reconnection: A Variation of the Phenomenological description of color reconnection between final state particles. M top = (172.6 ± 0.9 stat ± 1.2 syst ) GeV/c 2 Added here for the First Time !! Top Mass measurement Combination

Top Mass measurement New Result Template Method 3.0fb -1 : l+jets Mtop = ± 1.5 (stat.+JES) ± 1.1 (syst.) GeV/c 2 M top = (172.1 ± 7.9 stat ± 3.0 syst ) GeV/c 2 Lepton Pt 2.7 fb -1 Mtop = ± 0.9 (stat.) ± 0.7 (JES) ± 1.1 (syst.) GeV/c 2 Δ JES = 0.40 ± 0.26 σ Matrix Element 3.2fb -1 M top = ± 1.7(stat.) ± 1.9(syst.) GeV/c 2 All Had. 2.9fb -1 : template with NN selection

Top Cross section top =175 GeV σ pre = 6.7 ± 0.8 stat ± 0.4 syst ± 0.4 lumi pb. Di-lepton : 2.8 fb -1 σ tag = 7.8 ± 0.9 stat ± 0.7 syst ± 0.4 lumi pb. σ ttbar = 7.08 ± 0.38 (stat) ± 0.36 (syst) ± 0.41 (lumi) pb Lepton+jets with NN : 2.8 fb -1 Uncertainty is dominated by Luminosity Using ratio of σ ttbar /σ Z 6%(lumi)->2%(theory)

Following pages describe more detail

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dileptons 6%  had+e/μ 4% lepton+jets 34%  had+jets 10% all jets 46% Top Quark Decay Product

Jet Clustering and energy correction Clustering Summing tower energies in ΔR( ) =0.4 Correction Relative correction Minimum bias correction Absolute value correction Underling event correction Out of cone correction

New Physics Phenomena in  s -  t plane << SM|V tb |<1 (+) SMH ±,W’

S-channel optimization search t-channel s-channel top pair Tevatron1.98 pb0.88 pb6.7 pb LHC250 pb11 pb870 pb It is possible to search s-channel using 2-b-tag information Sensitive to the new physics mainly theory with extra boson(W’,H ± ) Exactly the same final state as: WH->lνbb (Golden channel at Tevatron) It is difficult to search s-channel at LHC because…

Background Estimation (non W) MC based QCD(nonW) Modeled by - failed electron - non isolated muon - jet trigger event W+jets Pre-b-tag events fixed Missing Et data 2b-tagged events b-tagging W+jets : mistag weight W+bb, W+cc : HF fraction QCD(nonW) x mistag weight

The number of event prediction

Acceptance Gain for Muon Non-triggerd muon in Met+2Jets Trigger Muon Trigger event Lepton trigger requires CMU&CMP (CMUP) or CMX -> add CMU only, CMP only and so on… Single CDF Acceptance +30% Significance +15%

Systematic Uncertainty

Top Mass measurement with in-situ W->jj JES calibration 1 tag 2 tag MtopMjj Template Method Mtop = ± 1.5 (stat.+JES) ± 1.1 (syst.) GeV/c 2 Mtop = ± 0.9 (stat.) ± 0.7 (JES) ± 1.1 (syst.) GeV/c 2 Δ JES = 0.40 ± 0.26 σ Matrix element (Multi-variate) Method

Top Mass : Lepton Pt 2.7 fb -1 Muon data Electron data M top = (172.1 ± 7.9 stat ± 3.0 syst ) GeV/c 2

Top Mass : All hadronic 2.9 fb -1 Mtop Mjj 1 tag 2 tag M top = ± 1.7(stat.) ± 1.9(syst.) GeV/c 2

Summer 2008 Tevatron Future Precision & EWK fit.

σ Z theory = ± 5.0 (sys) pb σ z measured = ± 1.01(stat) (sys) (lumi) pb 1/R = σ Z /σ ttbar = (stat) (sys) ttbar cross section using Ratio σ ttbar /σ Z σ ttbar measured =6.89 ± 0.41(stat) (sys) ± 0.14 (theory) pb σ ttbar measured =1/R x σ Z theory σ ttbar measured = 7.08 ± 0.38 (stat) ± 0.36 (syst) ± 0.41 (lumi) pb

W helicity 1.9 fb -1 the angle between the lepton as measured in the W rest frame and the W boson as measured in the top rest frame

F + = ± 0.04(stat) ± 0.03(syst)F 0 = 0.59 ± 0.11(stat) ± 0.04 (syst) F + < 95% C.L. Matrix Element method cos θ* template fit method f 0 = ± (stat) ± (syst) Assuming f + =0

Forward Backward Asymmetry 1.9 fb -1 Slightly positive AfbSlightly negative Afb

ttbar production mechanism 2.0 fb -1 Fgg= (stat.) (syst.) qq Spin gg anti-parallel spin state Spin parallel spin state J = 1 Jz =  1 qq annihilation gg fusion J = 0 Jz = 0  PP l l Fgg = (stat+sys) 1.0 fb -1 Combination

Search for the FCNC top decay 1.9 fb -1 Searching t → Zq vertex in top decay Br(t → Zq) < 3.7 %

Search For Pair Production of Stop Quarks Mimicking Top Event Signatures Similar decay product as ttbar

Search for Heavy Top t'->Wq In Lepton Plus Jets Events in 2.8 fb -1 A Search for charged Higgs in lepton+jets tt-bar events using 2.2 fb -1 of CDF data etc……