1. The Search for the Higgs at the Fermilab Tevatron: Run 2 Higgs Gordon Watts University of Washington, Seattle May 10, 2001

2. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 2 The Run 2b Series UW is going to collaborate with D0 in building the inner most two layers of Si for the Run 2b detector Series of talks on that topic Archived on the Web: http://d0.epe.phys.washington.edu/Projects/layer0 Tianchi’s excellent talks on construction, operation, and history of Si Vertex Detectors So Far:

3. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 3 The Standard Model Fundamental particles 3 families of fundamental fermions quarks leptons q = 0 q = -1 q = 2/3 q = -1/3 e   udud everyday matter Color Charge (3) cscs tbtb Electric Charge u u d proton All Seen,  most recent discovery

4. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 4 Force Mediators W ±, Z 0 Weak Force  E&M Force gluon Strong Force (8) The g and the gluon are massless. W±W± Z0Z0 80.436 ± 0.037 GeV/c 2 91.1875 ± 0.0021 GeV/c 2 LEPII & TeV Measurments Where does this mass come from?

5. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 5 Boson Mass Initially Massless (Gauge Bosons) Quantum Corrections do generate some mass + +etc. Goldstone Bosons BUT Predicted Mass of the Z is of MeV order!

6. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 6 Generating Mass Two common ways to generate mass in the SM Strong-Interactions between new fermions Adds terms to the correct calculation Considered less likely Weakly Interacting, self coupling scalar field The Standard Model incorporates the second The minimum additions Doublet of two scalars Vacuum expectation energy – key contribution to W,Z Mass calculations One degree of freedom left over The M Z is now very close (91 GeV/c 2 ) The Higgs M H is the free parameter

7. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 7 Current Indirect Results The Higgs Mass indirectly affects the measured top and W masses CERN EWWG Even without discovery we know quite a bit about the Higgs H W WW “Radiative Corrections” CDF (GeV/c 2 ) D0 (GeV/c 2 ) MWMW 80.433 ± 0.079 80.482 ± 0.091 MtMt 176.1 ± 6.6 172.1 ± 7.1 With LEP,  W = 34 MeV/c 2

8. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 8 Direct Searches Discovery only when direct evidence seen Search Strategy depends on Higgs Mass Decay products depend upon the mass Collider Environment Background production! Production channel will determine background Determines backgrounds

9. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 9 SM Higgs Decay Excluded by LEP Know Higgs Mass Know Branching Ratios Character of decay is changing rapidly in Tevatron’s Search Region

10. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 10 SM Higgs Decay Modes M H = 130 GeV/c 2 M H = 110 GeV/c 2 Topology of decay is changing rapidly Higgs/SUSY Working group Report

11. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 11 At LEP Production e + e -  HZ e + e -  WW e e  H e e The L3 events we are waiting on… Search Channels Defined by the Z decay 4 jet (qqbb),     bb, e + e - bb, etc. In their mass region, H  bb almost 80%. Backgrounds Detector backgrounds, QCD production, l + l - qq, qq 

12. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 12 LEP Direct Search Results No Discovery But tantalizing hints! No Discovery But tantalizing hints!  Lower limit is 113.5 GeV/c 2 Combined LEP Result Excess of 3  ALEPH 4j, 2j+mE T, 2j2 l Excess: 3.9  xsec: to high by ~2  e + e -  HZ

13. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 13 Direct Searches at the TeV QCD 2j background Associated HW, HZ production Light Higgs Heavier Higgs W*W (SM) Use gluon fusion! Search Strategy: bb decay: M H ~< 120 W * W decay: M H ~> 130 SM Higgs Production

14. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 14 Background Comparison M H (GeV/c2) ggWH+ZH 110900352 130558197 Events in one fb -1 Light Higgs gg  H  bb 2 jet topology Swamped by QCD di-jet background! ZH,WH  llbb, bb, l bb, jjbb BackgroundsEvents WZ+ZZ4400 Wbb+Zbb14000 tt7500 WW10400 QCD 4-jet background will make jjbb difficult! Heavy Higgs W*W 2 lepton & mE T, lepton & mE T & 2 jet, 4 jet lepton & mE T & 2 jet has large ttbar, WZj

15. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 15 The Analysis MC Signal & Background Raw Data (light Higgs) Trigger Isolated Lepton Event Selection High P T Lepton, W B Jet ID Low & High Quality JJ Mass Remove QCD BG Data JJ Mass Plot ZH,WH  llbb, bb, l bb, jjbb WZ+ZZ  lljj tt  l bbqq Wbb+Zbb  l bb, llbb QCD bb  bbl (fake or b) JJ Mass Plot Same Process Compare with statistical tools, look for the mass bump, mass windows, etc.

16. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 16 Run 2 at the Tevatron Energy now at  s 1.98 TeV 20% Increase in associated H production Larger pbar bunches x10 Larger Instantaneous Luminosity New Tracking, EM ID, readout New Tracking, EM ID, readout

17. Run 2 has started… (March 1 st, 2001) Collisions!

18. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 18 Run 2: Detector Upgrades Both CDF & D0 have had extensive upgrades Quick Scan of the final states –B-quark tagging Increased coverage, layers of Si –2jet mass resolution Preshower, tracking, larger samples for jet energy calibration –Lepton ID Increased coverage –Missing E T No large improvements expected What can you Expect?

19. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 19 Current Upgrade Status At the TeV Run 2 has started –Detectors are mechanically complete –Still installing and building electronics –Had a store of 36x36 (bunches). Final configuration. We have seen tracks! –Focus is now on improving the luminosity Radiation Losses At D0 several weeks ago

20. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 20 Tracks! Si Only xy view Andy Haas Elastic Tracker Tracks whole detector at once 20% of our Si tracker cabled

21. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 21 Combined Track Run 119679 Event 238687 First 36x36 Store Silicon Tracker Fiber Tracker

22. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 22 Run 2 Predictions Predictions from a series of Run 2 workshops –EW, Top, Higgs/SUSY –Work of almost 100 people Monte Carlo’s used were not Run 2 detector simulators –Parameterized MC Next Task for CDF & D0 –Bring up experiments –Calibrate detector simulations with real data –Start searches Repeat efficiency & acceptance studies Invent new techniques! –Higgs/SUSY was optimistic already

23. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 23 Run 2 Predictions 1.Detector efficiencies were extrapolated from Run 1 –Increased detector coverage was accounted for –3d tracking where we once had 2d (b-tagging) –Average Calorimeter/jet resolution for the two detectors (D0 is better) –Some assumptions are optimistic (jj resolution). No careful accounting for Multiple Interactions 2.Calculate efficiencies, acceptances –Luminosity required for discovery, 95% CL limit, etc.

24. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 24 Jet-Jet Resolution Crucial for Light Higgs Discovery Higgs/SUSY Report Better Energy Scale Better Jet Algorithms  corrections A lot of work to do…

25. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 25 B Jet Tagging Displaced tracks are most powerful indicator Use likelihood and NN to combine other event features Jet P T Track charge/multiplicity Width Relative P T ’s/SLT Secondary Primary

26. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 26 B Tagging Recent BID review: Got tagging rate Background rate needs work

27. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 27 Backgrounds Effort underway to calculate background rates to NLO Ellis, Cambel, Veseli hep-ph/0006304 No QCD background No detector effect

28. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 28 SM By Channel Two Search Stradegies Put it together

29. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 29 SM Higgs Search (2003) (2006) Does not include ttH. The two experiments combined

30. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 30 Detector Effects Achieving this will require a long-term effort Accelerator will change over the course of time Dead Silicon (radiation damage) Large effort underway to replace Consequences: 3.5 fb -1 8 fb -1 13.5 fb -1 19 fb -1 L1 & L2 will die Due to construction, and length of shutdown, faster/cheaper to replace whole detector!

31. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 31 Instantaneous Luminosity Steady increase in delivered luminosity Instantaneous luminosity increases Tevatron Collides bunches Number of minimum bias events Can separate in z Increase bunch size Increase # of bunches

32. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 32 Multiple Interactions Tevatron Collides bunches 1 Hard Scatter (Higgs production) Number of minimum bias events Can separate in z Beam Tilt in Z LHC Can simulate a displaced vertex! 3D Tracking Confusion in the tracker, trigger Better Tracking (pitch, etc.) 5E32

33. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 33 Conclusions The Higgs Search is a long term one –It will take us 2 years to rule out M H = 115 GeV/c 2 at 95% CL. –5  discover of 115 GeV/c2 is just within our reach, according to study Will have things to say about MSSM –Light sparticle searches –Indirect measurements Pushing edge of promised luminosity –Will press for more luminosity –Will look for improved experimental techniques! First Conference Results: Spring 2002

34. Higgs in Run 2 at the Tevatron Gordon Watts gwatts@fnal.gov University of Washington, Seattle May 10, 2001 34 Run 2 Indirect Results With 2 fb -1 of data (~2 years)  M W ~ 40 MeV/c 2  M t ~ 2.5 GeV/c 2 (per experiment)  M H ~ 80% M H Top will not by statistics limited Large Top dilepton samples Large W statistics Split W samples to study systematics Better detectors -> better energy scale measurement 2-3 Years (continuous)