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2 Tevatron Run II 1fb -1 per experiment on tape ~1.3 fb -1 delivered luminosity Peak luminosity 1.7 x cm -2 s -1 Presented here: ~ 700 pb -1 Goal of Run II per experiment:

3 Top production and decay 85% 15% Production: mainly Decay: BR(t  W b) ~ 100% All-hadronic: 44% Lepton + jets: 30% Dilepton: 5%

4 Why measuring the top mass? related to Top mass is related to W, Higgs W, Higgs (and other observables) When all W, t, H measured: test SM (and to test you have to measure well…) Radiative corrections affect observables Game of ElectroWeak fits

5 Mass Measurement Methods Template Method Matrix Element Method All methods in all channels are well validated by a blind sample Pick a test statistic (e.g. recontructed mass) Create “templates” using events simulated with different m t values (+background) Perform maximum likelihood fit to extract measured m t Build likelihood from matrix element(s), PDFs and transfer functions (connect quarks and jets) Integrate over unmeasured quantities (e.g. quark energies) Calibrate measured m t and uncertainty using simulation Less assumptions / robust measurement Better statistical precision expected w/ using more info

6 Likelihood Fit Parameterize Datasets Data Background MC ttbar MC Mass fitter Mass Fitter Finds best top mass and jet-parton assignment One # per event based on overconstrained system Additional selection cut on resulting  2 W->jj dijet mass distribution is a resonance Resonance peaks stands out at 80.4 GeV/c 2 Sensitive to shifts in jet energy scale (JES) M top template m top reco m jj template Parametrizations For both templates, as a function of top mass and JES For both signal and background Likelihood Fit Fit m top reco and w jj distributions in data to sum of signal and background parametrizations Constrain background and JES with prior knowledge gives JES, top mass! CDF Template Method : l+jets

7 m t reco templates w/ fit overlaidm jj templates w/ fit overlaid M top = ± 2.5 (stat. +  JES ) GeV/c 2  JES = -0.3 ± 0.6 (stat. + M top )  c 318 pb -1 : M top = (stat. +  JES ) GeV/c 2 Miscalibration in units of  c, external calib. CDF Template Results (I) 680 pb -1

8 CDF Template Results (II) Systematic  M top (GeV/c 2 ) Residual JES0.7 B-jet energy scale 0.6 Bkgd JES0.4 Bkgd Shape0.5 ISR0.5 FSR0.2 Generators0.3 PDFs0.3 MC stats0.3 B-tagging0.1 TOTAL1.3 Likelihood contours in M top -  JES plane

9 CDF Matrix Element Method: dileptonic channel The complete information contained in an event (x) regarding the top mass can be expressed as the conditional probability: If the momentum of each parton could be exactly deduced from final-state particles, the calculation of d  /dx would be simple. Instead we must integrate over quantities which are unknown and, in addition, quark energies are not directly measured. The total expression for the probability of a given pole mass for a specific event can be written:

10 CDF Matrix Element results Best measurement in challenging dilepton channel Could reach 2 GeV (stat) sensitivity by end of run II 750 pb -1

11 Template Method: l+jets M top =  4.2 (stat)  6.0 (syst) GeV/c 2 Event-by-event M top by  2 fit Use 69 candidate events with  1 b-tagged jet 370 pb -1

12 Combination of CDF and D0 Top Mass

13 Top Pair Production Cross Section  tt is crucial: Check of perturbative QCD Window to NP Look at all possible channels Starting point for all properties analysis tt is background of searches  inel =70mb so 7M events/s at /cm 2 s but 1 tt in events Need better quality M top (GeV/c 2 ) M. Cacciari et al. JHEP 0404:068 (2004) N. Kidonakis and R. Vogt, Phys. Rev. D (2003)

14 Dilepton Channel Selection: 2 leptons E T >20GeV with opposite sign >=2 jets E T >15GeV Missing E T >25GeV (and away from any jet) H T =p Tlep +E Tjet +ME T >200GeV Z rejection  (tt) = 8.3 ± 1.5 (stat) ± 1.0 (syst) (lumi) pb Backgrounds: Physics: WW/WZ/ZZ, Z   Instrumental: fake lepton

15 Lepton+Jets Channel: Kinematics Selection: 1 lepton with p T >20GeV/c >=3 jets with p T >15GeV/c Missing E T >20GeV Backgrounds: W+jets QCD discriminate spherical energetic central 7 kinematic variables in neural net  (tt) = 6.0 ± 0.6 (stat) ± 0.9 (syst) pb binned likelihood fit

16 All Hadronic Channel Selection: >=6 jets with pT>15GeV/c >=1 b tagged NN discriminant > 0.9 Huge QCD background ! discriminate 6 kinematic variables in neural net

17 Summary of Top Pair Production Cross Sections

18 Conclusions The top mass is now know with an accurancy of 1.3%, limited by the systematic uncertainties which are dominated by the jet energy scale. With in situ JES calibration, dominant “systematic” now scales as 1/sqrt(N). Expect 2 GeV/c 2 precision by LHC turn-on. All the cross section measurements are consistent with SM

19 Back up slides

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21 History of M top measurement Top first observed at CDF & D0 in Tevatron’s Run I: ~110pb -1 Run I Average: M top =  4.3 GeV/c 2

22 Jet Energy Corrections The jet energy scale (JES) is the major source of uncertainty in the top quark mass measurement and inclusive jet cross section Absolute scale: the jet energy measured in the calorimeter needs to be corrected for any non-linearity and energy loss in the un-instrumented regions of each calorimeter (from MonteCarlo) Relative scale: since the central calorimeters are better calibrated and understood, this scales the forward calorimeters to the central calorimeter Scale (is obtained using Pythia and data di-jet events) Multiple interactions: the energy from different ppbar interactions during the same bunch crossing falls inside the jet cluster (from minimum bias data) Underlying event: is defined as the energy associated with the spectator partons in a hard collision event. Out-of-cone: corrects the particle-leve energy for leakage of radiation outside the clustering cone used for jet definition

23 The total systematic uncertainties in the central calorimeter are the same order than RunI (significant improvement with respect 2004 analyses) Big improvements for plug jets with respect to RunI due to new detectors ~3% jet pT uncertainty in top events

24 Matrix Element Technique: dilept Harder to reconstruct M top in dilepton events: two neutrinos make system underconstrained Determination of probability is similar to l+jets No W resonance  no fit for JES Approximations have significant effect MC calibration essential Correct fitted mass for slope 0.85 Correct for pull width of 1.49

25 Matrix Element Technique: l+jets Calibrate method against MC samples Shows unbiased measurement Error are rescaled to account for observed pull width—due to approximations in integration

26 Matrix Element Results JES here is constant multiplicative factor E data = E MC /JES JES = 1.02 ± 0.02 Consistent with template method Virtually identical sensitivity with fewer events! 750 pb -1

27 Combination of CDF results Use BLUE (Best Linear Unbiased Estimator) technique NIM A , A Accounts for correlations in systematics Stat correlations in progress So far only combine measurements on independent datasets.

28 Decay Length Technique Difficult, measure slope of exponential But systematics dominated by tracking effects  small correlation with traditional measurements! Statistics limited now Can make significant contribution at LHC B hadron decay length  b-jet boost  M top 680 pb -1