1. Higgs to  at CDF Amit Lath Rutgers University Tev4LHC Workshop, Sep 17 2004

2. MSSM Higgs Production MSSM Higgs is produced copiously! (at reasonably large tan  ) Two main channels: -bb  A NLO from Maltoni, Sullivan, Willenbrock NNLO from Harlander, Kilgore - gg  A HIGLU (NLO) program from M. Spira Do the math : For M A =120 GeV/c 2, tan  =30:  (bb  A) = (8.9e-3)(30) 2 = 8.0 pb  (gg  A) = 5.2 pb  = 13.2 pb ~2500 A produced with 200 pb -1 ! (x2 more if you consider h as well)

3. Higgs Decays Higgs decays primarily to bb (~ 90%) - HUGE background from strongly produced bb. So what can we do? 1) Look for associated production - associated with W, Z Yoshio Ishizawa’s talk - with a 3 rd, 4 th b-quark. Avto Kharchilava’s talk 2) Look for other higgs decays: -  is promising (down by x10, but only Weak bgs) -  Sungwon Lee’s talk

4. How to get  Trigger on isolated “pencil jets” hadronic  decays (  h ) Ask for an e, , [or 2 nd (  h ) ] in event. 1 or 3 tracks e or   decays   e e  ,     : leptonic decays (~36%).  ,   ,  , … : hadronic decays (~ 64%). 1 st time at hadron collider! (to be added to higgs search)

5. The Trouble with  QCD jets! They can look like  h Fight with: energy, isolation. Triggered  h object: - cluster-matched track with p T > 4.5 GeV. - no tracks w/ p T > 1.5 Gev in 10-30 0 iso. annulus. -Electron +  h  central electron (E T > 8 GeV) +  h object (~30nb at L3) -Muon +  h  central muon (p T > 8 GeV) +  h object (~30nb at L3) -  h +  h  two  h objects, with extra L2 isolation (~13nb at L3) LHC take note! constant trigger rate battles! Not yet included in MSSM higgs search.

6. Reconstructing  h Tighten isolation. Reconstruct  0. - use EM calorimeter for  energy. - use ShowerMax for  position. Remove electron candidates. m trks+   < 1.8 Look for characteristic 1, 3 track enhancement. Signature of hadronic tau decay! 2  clusters 1  cluster +  +-

7. Background Removal |P T  1 | + |P T  2 | + |E T | > 50 GeV Jets tend to be soft. Requiring scalar sum of energy of objects in event > 50 GeV further reduces backgrounds.

8. W associated backgrounds Define:  – vector: Bisector of visible  dirs P vis   project VISIBLE  ’s onto  P      P vis        W+jet events  E T more back-to-back with jets.

9. Hadronic  signature Nice 1, 3 track enhancement. Only 1,3 track events. Only events with  h, e/  opp. Charge. Jet   fakes under good control!

10. Hadronic  distributions Low levels of jet  t fakes (~0.1% at higher p T ) Good agreement in E T H T above cut of 50 GeV Fakes well understood. Long-standing discrepancies between jet samples resolved. (Run 1  fakes ~ 1%)

11. Predicted vs. Observed Events source eheh hh combined Z/  * →  132.3±17.1104.1±13.3236.4±29.5 Z/  * → ee,  1.8±0.24.9±0.46.7±0.6 VV, tt0.7±0.10.8±0.11.5±0.1 Jet →  fakes 12.0±3.67.0±2.119.0±5.7 Total predicted BG146.8±17.5116.8±13.5263.6±30.1 Observed133103236 CDF Run 2 Preliminary (195 pb -1 )

12. MSSM Higgs Signal Pseudo scalar MSSM Higgs generated with tan  =30 used as acceptance model. Define m vis = m(p(  1 ) + p(  2 ) + p(E T )) Where p(E T ) = (E X,E Y,0,E T )

13. Z/Higgs Separation Binned likelihood fit shown with m A = 130 GeV component in yellow Normalized to 195 pb -1 No Higgs component Lum, Z-xscn, bg, all fixed w/in errors. Linear Semilog

14. Fit Results From pseudoexperiments

15. Fit Results Very conservative treatment of energy scale shift causes poor limit at low mass.  will get better.

16. Limit Table Need NLO calculation of higgs production to get exclusion in M, tanb plane.

17. What’s Next? Have > x2 luminosity on tape already. Understand energy scale better, limits (esp. at lower mass) will get better. Will add  h  h (ditau),  e   channels – Ditau adds stats similar to  e  h channel. –  e  m small, but very clean. Also looking at: –Additional jet with b-tag. –Extending acceptance into plug region. –Neural nets for reconstruction. First time at hadronic collider.

18. Conclusion Direct Search for A   performed at CDF Didn’t find evidence of higgs, but… – achieved excellent acceptance – lower than expected jet   fake rates CDF expects ~ 4 fb -1 of data by end of Run 2 – if MSSM higgs exists (at higher tan  ) we will see it!