Recent Results from the Tevatron

1. Recent Results from the Tevatron Mary Convery Fermilab for the CDF and DØ Collaborations ALCPG11 – Linear Collider Workshop of the Americas Eugene, Oregon March 19-23, 2011

2. Outline • Introduction • Recent Tevatron highlights • New particles observed • CP violation • Precision measurements • Higgs searches • Conclusions ALCPG11

3. The Fermilab Tevatron Collider Run II Proton-antiproton collisions at √s=1.96 TeV Chicago CDF DØ Proton source Tevatron ( ~4 miles circumf) Antiproton source Main Injector / Recycler ALCPG11

4. The Fermilab Tevatron Collider Run II Tevatron has performed well the last few years Optimized use of antiprotons Integrated luminosity (pb-1) / 1013 antiprotons year ALCPG11

5. Luminosity performance and projections on track for ~12 fb-1 through FY11, experiments would acquire ~10 fb-1 ~12 fb-1 currently ~10.5 fb-1 9.305 fb-1 delivered thru FY10 9.3 fb-1 7.8 fb-1 Integrated luminosity (fb-1) real data for FY02-FY08 have achieved design parameter goals of Run II - - - - - - - - - FY04 FY05 FY06 FY07 FY08 FY09 FY10 FY11 ALCPG11

6. CDF and DØ Run II detectors • Both detectors • Silicon microvertex tracker • Solenoid • High rate trigger/DAQ • Calorimeters and muons L2 trigger on displaced vertices Excellent tracking resolution Excellent muon ID and acceptance Excellent tracking acceptance || < 2-3 ALCPG11

7. The Tevatron research program Precision, New Research Discoveries Unique Window into the unknown Searches for Supersymmetry, Extra Dimensions, Exotica Probing the Terascale as the luminosity increases Standard Model Higgs Boson is within reach! • Mixing, CKM Constraints and CP Violation • Heavy Flavor Spectroscopy • New Heavy Baryon States • Tests of Quantum Chromodynamics • Precise measurement of Top-quark and W-boson Masses • Top Quark Properties • Di-Boson production and SM Gauge Couplings • New Exclusive/Diffractive Processes ALCPG11

8. Observation of new heavy baryons dsb ddb uub ddb uub dsb ssb 2007 2006 2009 ALCPG11

9. With more data: emergence of a new particle (CDF) Y(4140) unknown composition 2009 • m  = 4143.4+2.9-3.0 (stat) ± 0.6(syst) MeV/c2 •   = 15.3+10.4-6.1 (stat) ± 2.5(syst) MeV/c2 • statistical significance > 5s These new discoveries yield a few events/fb-1 new areas of research @ 10 fb-1 ALCPG11

10. CP violation • Charge-conjugation – Parity conservation: a process in which all particles are exchanged with their antiparticles is equivalent to the mirror image of the original process • The weak interaction does not conserve C, P, or CP, so the Standard Model predicts CP violation • Cabibbo-Kobayashi-Maskawa matrix contains information on the strength of flavor-changing weak decays, important in the understanding of CP violation • CKM matrix unitary in the SM SM levels of CP violation do not explain apparent matter-antimatter asymmetry of the universe ALCPG11

11. CP violation in Bs→ J/y f _ _ • The mass eigenstates are a superposition of Bs and Bs • Width difference between mass eigenstatesDG is correlated with bs • Measure simultaneously • CP violation in the interference between decay w/ and w/o Bs - Bs mixing • Measure by statistical determination of CP even and odd contribution using angular analysis • New physics can have large effect on CP violation Bs0=sb Bs0=sb f J/y _ _ Bs0 Bs0 J/y f _ _ Bs0 _ ,t’ ,t’ ALCPG11

12. Precision: CP Violation in s Both CDF and D0 measure the CP violating parameter s in Bs in J/ ALCPG11

13. Dimuon charge asymmetry (D0) • Measure CP violation in mixing using the dimuon charge asymmetry of semileptonic B decays: • Nb++, Nb−− : number of events with two b hadrons decaying semileptonically and producing two muons of same charge • One muon comes from direct semileptonic decay b → μ−X • Second muon comes from direct semileptonic decay after neutral B meson mixing • Evidence for anomalous like-sign dimuon charge asymmetry • Asl is 3.2s from Standard Model predictions • First evidence for Beyond the Standard Model CP Violation ALCPG11

14. Measurement of time-integrated mixing probability of B hadrons • Double semileptonic decay of BB results in OS lepton pair when no mixing; LS lepton pair when one meson undergoes mixing • Use impact parameters of muon pairs with template fits to identify source of muons: b, c, prompt • Correct for other sources of dimuons • c=0.126±0.008, consistent with LEP average c=0.1259±0.0042, smaller than previous Tevatron measurements (CDF’s used looser silicon-track requirements) _ μ μ μ+ μ+ _ _ μ+ μ ALCPG11

15. Search for new dielectron resonances and Randall-Sundrum gravitons • Common approach to search for new particles – look for bump in mass of combined objects • No significant excess over SM observed • Combined with 5.4 fb-1 diphoton analysis, RS-graviton mass limit for the coupling k/MPl=0.1 is 1055 GeV/c2 – strongest limit to date Highest-mass dielectron ever observed (960 GeV/c2) ALCPG11

16. Signature-based Search:γ+ missing-ET + b-jet + lepton • Search for new physics by looking for anomalies in kinematic distributions, rather than limiting search to specific model • Leading background is Standard  Model  ttg • No excess observed • Measure cross section σ(ttg) =0.18 ± 0.07 pb • R(ttg /tt) = 0.024 ± 0.009 ALCPG11

17. Towards the Higgs ALCPG11

18. W mass summary Tevatron has world’s best measurement Mw = 80.399  0.023 GeV ALCPG11

19. Top quark pair production and decay • Top quark existence required by the SM, partner of the bottom quark • Discovered in 1995 at Tevatron • Only SM fermion with mass at the EW scale ~40x heavier than the bottom quark • Top decays before hadronization – provides unique opportunity to study a "bare" quark • Pair produced via strong interaction • Top quark decays ~100% to W+b • t-tbar events classified by decay of W’s: • All-hadronic (44%, large background) • Dilepton (5% excl t, small background) • Lepton+Jet (30% excl t, manageable background) ALCPG11

20. Summary of Top Mass updated new! We now know the mass of the top quark with better precision (<1%) than any other quark ALCPG11

21. Constraints from precision top quark mass measurement X ?? • SM Higgs Mass constrained by Mtop and MW through loop correction of W mass • Precision top quark mass measurement • Predict SM Higgs mass • Constraints for physics beyond standard model ALCPG11

22. Where is the Higgs hiding? MH < 157 GeV at 95% C.L. preferred MH – 87+35-26 GeV Mw vs Mtop ALCPG11

23. Standard Model Higgs production and decay • Higgs are produced in several different ways • gg→H, qq → WH, qq → ZH biggest cross sections • Also qq → qqH, bb → H, gg,qq→ ttH • The Higgs decays into different “final states” depending on its mass • To find it, we need to look at all these final decay states and combine the results ALCPG11

24. The Challenge # of Events produced/exp in 1 fb-1 These are production numbers – trigger, acceptance etc. not yet factored in… ALCPG11

25. W/Z + jets • Test of perturbative QCD • Background for W/Z+H and other new physics • Test Monte-Carlo modeling ALCPG11

26. ALCPG11

27. Di-bosons WW, WZ, ZZ • Background to Higgs searches: W/Z H, H->WW, H->ZZ • Similar techniques as used for Higgs searches • dijet mass, matrix element, neural networks • Discrimination in kinematics of final state (???) ALCPG11

28. WW/WZ → lepton + jets • Using mjj and matrix element techniques with 4.3-4.6fb-1 • Observed with >5s significance 5.4 σ 5.2 σ σ = 18.1 ± 3.3stat ± 2.5sys pb SM = 15.1 ± 0.9 pb σ = 16.5 +3.3-3.0 ± 3.5sys pb ALCPG11

29. WZ→llln, ZZ→llnn • Using neural networks 3.7±0.6(stat.). +0.6-0.4 (syst.) ALCPG11

30. ZZ → eeee, eemm, mmmm • 10 events • σ = 1.35+0.50-0.40(stat) ± 0.15(syst) pb • SM prediction 1.4±0.1 pb ALCPG11

31. Single top • Test s vs t channel [new physics] • Direct measurement of Vtb [precision] • Lifetime [new physics] • Wbb similar final state as Higgs • Similar tools ALCPG11

32. SM Higgs: HWW (high mass channel) W+ H μ+ W+ W- ν e- W- • HWWll - signature: Two high pT leptons and MET • Primary backgrounds: WW and top in di-lepton decay channel • Key issue: Maximizing signal acceptance • Excellent physics-based discriminants • Most sensitive Higgs search channel at the Tevatron ν Spin correlation: Charged leptons go in the same direction ALCPG11

33. Limits from HWW • First time CDF and D0 independently exclude mass range for Standard Model Higgs at 95% CL • D0 excludes MH=165 GeV/c2 • CDF excludes 158<MH<168 GeV/c2 ALCPG11

34. Combine experiments Neither experiment has sufficient power to span the entire mass range using the luminosity we expect to acquire in Run II Factor away in sensitivity from SM SM Higgs Excluded: mH = 163-166 GeV ALCPG11

35. We are making steady progress… • Some projected improvements: • Combine all channels • Maximize signal acceptance • Improve b-tagging to reduce W/Z+jets background • Improve dijet mass reconstruction (resolution) • Improve di-tau mass reconstruction • Improve signal vs background separation (neural networks, boosted decision trees, matrix element methods, combining different kinematic variables ALCPG11

36. How well can we do? ALCPG11

37. _ Forward-backward tt production asymmetry • QCD t-tbar production symmetric at leading order, positive and negative contributions to asymmetry at next-to-leading order • Asymmetry seen in previous measurements by CDF and D0 and dilepton channel • New CDF measurements show 2s excess in both lepton+jets and dilepton channel low mass high mass high mass l - high mass l + ALCPG11

38. Evidence for mass dependence of Afb • Significant asymmetry at large Dy, Mtt • Consistent with CP conservation (l + vs l - = t vs t) low mass high mass high mass l - high mass l + _ ALCPG11

39. Conclusions • The Tevatron has a broad program • Precision measurements • Mixing, CKM Constraints and CP Violation • Precise measurement of top-quark and W-boson masses • Searches for Higgs and beyond SM physics • B hadron spectroscopy • Once new particles observed, studies of their properties • Tests of Quantum ChromoDynamics • Stay tuned as the Tevatron continues to produce important results in many areas of HEP ALCPG11