RECENT CDF RESULTS ON THE TOP QURK Nikos Giokaris University of Athens On behalf of the CDF Collaboration September 21, 2006

Crimea 2006, 9/21 N. Giokaris 2 OUTLINE I.TEVATRON PERFORMANCE II.CDF DETECTOR III.TOP QUARK I.Discovery II.Production & Decay III.Top quark Properties I.Cross section II.Top mass III.W helicity in Top decays IV.Search for Single Top V.Search for Resonant Production IV.Conclusions

Crimea 2006, 9/21 N. Giokaris 3 Run II with Record peak Luminosity: 2.3x10 32 cm -2 s -1 Integrated delivered luminosity: 1.5 fb -1 CDF recorded luminosity: 1.3 fb -1 TEVATRON Performance Expected: 2fb -1 by fb -1 by fb -1 by 2009

Crimea 2006, 9/21 N. Giokaris 4 CDF Detector

Crimea 2006, 9/21 N. Giokaris 5 Top Quark History Searched for since the late ‘70s, after the discovery of the b quark Discovered by CDF and D0 in 1995 (Run I) –∫Ldt~100pb -1 –Mass ~175 GeV –Decays to Wb, as M top >M W –ttbar Cross Section 7.6pb

Crimea 2006, 9/21 N. Giokaris 6 Top-Antitop Production and Decay Half-life of top: ~ s Top decays before hadronizing! e-e(1/81) mu-mu (1/81) tau-tau (1/81) e -mu (2/81) e -tau(2/81) mu-tau (2/81) e+jets (12/81) mu+jets(12/81) tau+jets(12/81) jets (36/81) W bosons decay either hadronically or leptonically. W decays define channel: Dilepton: 12% Lepton+jets: 44% All-hadronic: 44% Strong Production NLO) dominates at Tevatron Energy 85%: 15%:

Crimea 2006, 9/21 N. Giokaris 7 Top Cross Section M top s NLO (pb) ± ds ± ± ±0.7 Theoretical predictions Measured in all topologies. Use complementary techniques: topological (counting) vs shape fit. Deviation from SM expectations could indicate non-SM production mechanism or new physics in top sample.

Crimea 2006, 9/21 N. Giokaris 8 How we measure Top Top decays before hadronizing: Observed through W decay products  leptons (Lepton +Jet and Dilepton channels)  Jets (problem with jet combinations) Two methods to measure top: 1.Use b-tagging  Good S/B  Lose ~50% in efficiency 2.Use kinematics (NN, etc)  Also good S/B

Crimea 2006, 9/21 N. Giokaris 9 L+jets channel: Large BR ~44% and Good S/B Lepton+Jets Cross Section Results in 750 pb -1 Lepton + MET + ≥1b-tag

Crimea 2006, 9/21 N. Giokaris 10 Dilepton Cross Section Result in 750 pb -1 Dilepton channel: Small BR ~5% for e and μ leptons BUT Easy to identify e and μ Very good S/B

Crimea 2006, 9/21 N. Giokaris 11 All Hadronic Cross Section Result in 1 fb -1 L+jets channel: Large BR ~44% but Poor S/B

Crimea 2006, 9/21 N. Giokaris 12 Cross Section Summary NOW REACHED 12% pb -1 Expected  10% uncertainty/experiment with 2fb -1 We are doing much better than predicted in TDR!!

Crimea 2006, 9/21 N. Giokaris 13 Top Mass Fundamental parameter of SM. Recent Tevatron combination: M top =171.4 ± 2.1 GeV EWK fit gives: In Run II, expect δM W = ±25MeV and δM top = ± 2 GeV  35% constraint on the Higgs Mass. Sensitive to new physics through radiative corrections

Crimea 2006, 9/21 N. Giokaris 14 Top Mass Measurement Mass measurement is hard Jet combinatorics ISR/FSR jets Jet Energy Scale (JES) uncertainty Two methods Template Methods Matrix Element Method (ME) The idea in both methods is try to reconstruct the parton level quantities

Crimea 2006, 9/21 N. Giokaris 15 Top Mass with Template Method 1. Evaluate event-by-event best “reconstructed mass”, M rec, by using observed kinematics of ttbar event (e.g.: χ 2 fitter) 2. Create “templates”, i.e. MC predictions for M rec using different true masses of M top. 3. Measure top mass with likelihood fit of data M rec to signal + background template. Background

Crimea 2006, 9/21 N. Giokaris 16 Top Mass in lepton+jets JES uncertainties are the largest source of systematics: ±1σ JES  σ Mtop = ±3GeV Fit simultaneously for M W  jj and M bjj using 2D templates of true Mtop and σJES (940 pb-1) achieves world single best measurement with Matrix Element Analysis Technique (MEAT) Mtop = ± 2.2 (stat+JES) ± 1.4 (syst) GeV/c 2 =170.9 ± 2.6 GeV/c 2

Crimea 2006, 9/21 N. Giokaris 17 Top Mass with ME Calculate event-by-event signal probability curve (rather than single M rec ) using decay matrix element and transfer functions. Calculate event-by-event background probability (no dependence on Mtop!). Combine signal and background probability in one likelihood vs M top for entire sample ME method uses maximal information per event at a price of simplified assumptions. Final mass result and uncertainty is calibrated against simulated events.

Crimea 2006, 9/21 N. Giokaris 18 Top Mass in Dilepton Underconstrained system: two neutrinos but only one MET measurement. Remind that the major difficulty in reconstructing top is the parton-level cambinatoric problem (1 fb -1 ) assumes highest two E T jets are the b-jets and integrate ME probability over 8 unknowns Using 78 events (27.8 bkgr) –Confirmed in b-tag dilepton sample(S:B~30:1). –Consistent results in template measurements.

Crimea 2006, 9/21 N. Giokaris 19 Top Mass in All Hadronic Low S/B (~1/8) and large combinatorial background (90 permutations for 6 jets) Top Mass Measurement with Template method using NN Selection has -1 : M t = ± 2.2 (stat) ± 4.8 (syst) Gev/c2

Crimea 2006, 9/21 N. Giokaris 20 Top Mass Summary CDF -1 : M top = 170.9±1.4 stat ±1.9 syst

Crimea 2006, 9/21 N. Giokaris 21 Top Lifetime Top in SM has very short lifetime (SM ct ~ 3x μm) look for anomalous lifetime by fitting impact parameter of lepton in l+jets events ct<

Crimea 2006, 9/21 N. Giokaris 22 W helicity in Top Decays F 0 +F - +F + =1 Helicity states of the W: Because top is heavy: SM test: if V-A interaction F - ˜ 0.3 F + ˜ 0 if V+A interaction F - ˜ 0 F + ˜ 0.3 Top in SM has V-A decay. Longitudinal Left-handed Right-handed F 0 F - F + suppressed by factors of order m 2 b /m 2 t Variables sensitive to W helicity are angular distributions of W products in W rest frame. cos(θ*) distribution M 2 l b Lepton p T spectrum

Crimea 2006, 9/21 N. Giokaris 23 CDF has 3 measurements 1. cos(θ*) with full tt reconstruction in l+jets 2. M 2 lb in dil and l+jets 3. cos(θ*) in l+jet samples using the mass χ2 fitter W helicity measurements Assume V-A and measure F 0 /F - with other components fixed at SM value. Measure F + and put limits on V+A/new physics. 318pb pb pb -1

Crimea 2006, 9/21 N. Giokaris 24 Single top NLO σ t-channel1.98±0.25 pb s-channel0.88±0.11 pb Single top is produced via weak interaction at a rate ~1/3 that of top. Allows direct measurement of Vtb. B.W. Harris et al. Phys. Rev. D (2002) Kinematically wedged between non-top and top signal, plus high backgrounds (S/B~1/20) requires very sophisticated analysis techniques. Use l +MET+2jet (>=1 btag) events: same signature as s and t-channel searched jointly and separately (have different sensitivity to new physics). s-channel production (W*) V tb t-channel production (Wg fusion) V tb

Crimea 2006, 9/21 N. Giokaris 25 Single Top Limits CDF has 2 methods 1.Multivariate Likelihood Function 2.Neural Network Channels+tt(pb)s(pb) SM σ NLO 2.9±0.42.0±0.30.9±).1 Lhood σ 95% 4.3(3.4)2.9(2.6)5.1(5.7) NN σ 95% 3.4(5.7)3.1(4.2)3.2(3.7) 695 pb -1 95% observed (expected) exclusion limit getting close to SM expectations! Statistical errors only Based on SM single-top cross section Projections 2.4 s excess with 1 fb -1  expected by end of ‘06 3 s excess around 1.5 fb -1 (syst ignored)

Crimea 2006, 9/21 N. Giokaris 26 Search for Resonant Production Look for bumps in the ttbar invariant mass spectrum CDF looks for generic spin 1 resonance (X 0 ) Assume Γ X0 = 1.2%xM X0 (narrow resonance) Test masses between 450 GeV and 900 GeV in 50 GeV increments. Set 95% confidence level limit for σ X0 at each mass. Exclude leptophobic Z’ with M z’ < 725 GeV.

Crimea 2006, 9/21 N. Giokaris 27 Conclusions CDF II has used as much as x10 the RUN I statistics to perform several studies on the top quark –ttbar production cross section has been measured to about 12% level –Top mass precision is already known to ~1.5% level – expect to go down to ~1% by the end of RunII, thus further constraining the SM Higgs mass –Single top should be detected soon –All the, up to now, measurements show that top quark behaves as predicted by the Standard Model

Crimea 2006, 9/21 N. Giokaris 28 Acknowledgments R. Erbacher V. Giakoumopoulou T. Maruyama M. Tecchio