1 Higgs Searches at the Tevatron Chris Tully Princeton On behalf of the CDF/D0 Collaborations SUSY 2005 IPPP Durham, England, July 18-25, 2005

2 Low Energy Supersymmetry  The Higgs Sector is vacuous without it… Stability of the Electroweak scale is as fundamental and as deserving a resolution as Classical E&M arguments were to the instability of atomic states posed over a 100 years ago. We can only hope the answer will be equally far reaching…

3 Preferences from M W and m top  Error on m top no longer dominates  W self-energy may be decisive once M W improves M top = ± 2.9 GeV New CDF/D0 Mass Combination

4 New Top Mass Combination  This includes new preliminary measurements (based on 320 pb -1 ) from CDF/D0 which simultaneously fit the jet energy scale with the hadronic W mass constraint  The correlated systematical error is of order ~1.7 GeV

5 9 SUSY Guidance Lightest Higgs mass compatible with high tan  region for wide range of stop mixing Heinemeyer, Weiglein qd,ℓ–qd,ℓ– qd,ℓ+qd,ℓ+ h: H: A: Use tanβ enhancement! LEP Preliminary down- type

6 Large b-Production  But how well known… Use Leptonically Decaying Z’s as a probe! B-hadron Lifetime tag Z+b PRL 94, (2005) pb -1

7 MSSM Higgs b(b)  Search  b(b)  → b(b)bb  =h/A or H/A  At least 3 b-tagged jets  Data-derived background shape Leading Submitted to PRL 260 pb -1 at 95% Excl.

8 b(b)  Limits: tan 2 β Enhancement Enhancement depends on loop corrections (Δ b ) and SUSY parameters: 260 pb -1

9 b(b)  Projections CDF+ 1 fb -1 8 fb -1 4 fb -1 2 fb -1 Tevatron will probe below ! Projection based on existing analysis: Doesn’t include proposed b-tag improvements

10 Higgs Decays to  -leptons   -Identification Methods (CDF) Before OS req. Method yields a rich sample of taus with the expected visible masses and track multiplicities from Z → 

11 h/H/A →  Search  Visible Mass is the final search variable: tan  =30 H

12 MSSM Higgs →  Search  tan  Exclusion Limits: b(b) 

13 Higgs →  Projections  Higgs →  and b(b)  will reach similar sensitivities at the same time Opens up exciting prospects for learning more about SUSY as y b and y  see different loop-corrections Assumes several analysis improvements CDF+D0

14 Charged Higgs from top quark decay  Predicted to substantially modify top quark Branching Ratios at high and low tan   Additional sensitivity in lepton +  channel m H + = 100 GeV m H + = 140 GeV   cs t*bt*b

15 H + tan  Exclusion

16 Br(t → H + b) Exclusion for Br(H + →  )=1  Range of Exclusions Br<0.4 to Br<0.7 depending on MSSM parameters H + →cs Search in progress…

17 Lightest Higgs Boson Lightest Higgs boson is SM-like for large M A Given the difficulty of detecting the h→bb decay at the LHC, the Tevatron provides a potentially essential probe of this low mass channel (decoupling limit)

18 Low Mass Higgs Search  Maximum sensitivity requires a combination of CDF/D0 search channels:  WH →ℓ bb, ZH → bb & ℓℓbb, WH →WWW *, H→WW

19 ℓ bb Search (CDF) 319 pb -1

20 e bb Search (DØ)   bb in Progress… Expect 0.14 ± 0.03 WH 4.29 ± 1.03 Wbb 5.73 ± 1.45 tt+other Total 10.2 ± 2.4 events Observe 13 Tagged Sample ≥1 b-tag Double-Tagged Sample

21 Missing Energy Channel (CDF)  Two Control Regions:  No Leptons +  (E T, 2 nd Jet)<0.4 (QCD H.F.)  Min. 1 Lepton +  (E T, 2 nd Jet)>0.4 (Top, EWK, QCD) Control Region 1 Missing E T b-jet y x Large E T Two jets (one b-tagged)

22 Missing Energy Event (CDF) Second Jet E T = 54.7 GeV Leading Jet E T = GeV Double tagged event Di-jet invariant mass = 82 GeV Missing E T GeV

23 Missing Energy Channel (CDF) Selection cut ZH 120 (288.9 pb -1) Di-jet mass cut (100,140)  0.016

24 Missing Energy Channel (DØ)  Cross-efficiency important  WH → ℓ bb (lost ℓ)  ZH → bb  3x Larger WZ/ZZ Signal  Similar dijet bb mass peak

25 WH → WWW * (CDF) Vector p T Sum 2 nd Lepton p T Fake Lepton Region “One Leg” Photon Conv SM Signal Expected m H =160 GeV No Event Seen Same-Sign Dilepton Search

26 WH → WWW * (DØ)  WWW * → ℓ ± ℓ ± + X  Same-Sign Dileptons  Important bridge across GeV “Gap” from H → bb and inclusive H →WW  Background from WZ→ ℓ ℓℓ pb -1 CDF 194 pb -1

27 H → WW (DØ) Leptons from Higgs tend to point in same direction Apply  ℓℓ  < 2  ℓℓ  < 2 WW cross section measured PRL 94, (2005)  WW =13.8 (st.) (sy.) ± 0.9 pb – 3.8 – 0.9

28 Overview of CDF/DØ SM Higgs Searches

29 Prospects for SM Higgs Search  Current analyses sensitivities are lower than used for projections, but differences appear to be recoverable

30 Summary  MSSM tan  enhancement searches  b(b)  & Higgs →  already sensitive to tan  ~50-60  Plans to add b(b)  → b(b)   t → H + b, H + →  results (Plans to add H + →cs )  SM Higgs searches  Full complement of search channels with first results  Will be important to benchmark search sensitivity with WZ diboson production with Z → bb  ~1 fb -1 to analyze by Fall Combine, combine, combine…

31 Backup Plots & Tables

32 Tevatron Performance

33 SM Higgs Production Processes

34 Z → bb (CDF)

35 ℓ bb Search (CDF)

36 H → WW (DØ)

37 Improvements to b-tagging OperatingPoint ~ Fake Rate ~ b Efficiency Tight 0.25 % 44 % Medium 0.5 % 52 % Loose 1.0 % 57 % Loose % 64 % Loose % 68 % Loose % 70 %  Analysis depends on strongly on b-tag  Neural Net b-tagging DØDØ

38 Z →  as a benchmark  DØ Neural Network  -Selection  Variables:  Shower Profile  Calorimeter Isolation  Track Isolation  Charged Momentum Frac  Opening Angle  Etc.  3 Types:   -like   -like  Multi-prong

39 Missing Energy Channel (DØ) Trigger on event w/ large E T & acoplanar jets Instrumental E T backgrounds (Data-driven estimation) – –Asymmetries computed: Asym(E T,H T ) and Asym(  p T trk, p T2 trk ) Data Data in signal region Signal Sidebands Exponential Signal Instr. Background from Sidebands(Data)

40 Missing Energy Channel (DØ) No b-tag Single b-tag Double b-tag

41 H → WW (CDF) Cluster mass: =184 pb -1