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Gregorio Bernardi, LPNHE-Paris VI & VII

Status of Higgs Searches @ D Ø. Publications Publications to come, p17 prel. SM Higgs Searches at High mass Combined D0 and CDF+D0 results. Susy Higgs status Future plans. Gregorio Bernardi, LPNHE-Paris VI & VII. Publications. ‘03 : 1 H ++

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Gregorio Bernardi, LPNHE-Paris VI & VII

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  1. Status of Higgs Searches @ DØ Publications Publications to come, p17 prel. SM Higgs Searches at High mass Combined D0 and CDF+D0 results. Susy Higgs status Future plans Gregorio Bernardi, LPNHE-Paris VI & VII

  2. Publications • ‘03 : 1H++ • ‘04 : 2 WH, Zb/Zj(and WW x-section) • ‘05 : 2 bbh , H WW* • ‘06: 4 so far (based on 260-350 pb-1 of data) • h  t+ t- (includes combination with hbb) • WH  WWW* • ZH  n n b b • Z + n jets x-section

  3. P14 Publications coming SM: WH (e, m) (moriond) ZH  l+ l- b b (ee, mm) (ICHEP) SM combination (ICHEP) Z  bb (x-section) (ICHEP) SUSY: bbh with h  t+ t- (ICHEP) Technicolor: e and m channels (ICHEP)

  4. P17 Preliminary Results SM: Z+jets Sherpa study (moriond) H WW* (ee, em) (moriond) (mm) (ICHEP) Updated SM combination (+ CDF) SUSY bbh with hbb (ICHEP) In the works (cf Higgs p17 meeting tue/fri.) ZH  nn b b, ZH l+ l- b b (ee, mm) WH (e, m) h t t H+ (direct, indirect)

  5. SM “Heavy” Higgs: H  WW*  lnln e+ n W+ n W- e- Search strategy:  2 high Pt leptons and missing Et  WW comes from spin 0 Higgs: leptons prefer to point in the same direction. But Higgs mass peak cannot be reconstructed due to the presence of 2 nlook for an excess CDF and DØ already published on 0.3-0.4 fb-1 H 4th generation? Updated DØ analysis: L ~ 950 pb-1 in H  WW*  ee and em L ~ 930 pb-1 in H  WW*  mm • Selection : • Presection:lepton ID, trigger, opposite charge leptons • Remove QCD and Zl+l-:ET > 20 GeV • Higgs Mass Dependent Cuts:Invariant Mass (Ml+l-); Min. Transverse Mass Sum of lepton pTl and ET (S pTl + ET) • Anti tt(bar) cut: HT = S PTjet < 100 GeV • Spin correlation in WW pair:Df(l,l) < 2.0 Major backgrounds: WW production , W + jet/g production

  6. HWW* : final selection ee mm em selections MH=160GeV (x10)

  7. Results for HWW* Expected/Observed # of events for mH = 160 GeV (L ~ 950 pb-1): mm 9 9.8±0.8 6.6±0.1 1.0±0.4 0.6±0.4 0.5±0.1 0.5±0.1 0.6±0.6 0.35 mm If mH= 160 GeV,  ~ 2 higgs in our sample! SM only a factor 4 away We exclude 4th generation models, for which mH=150-185 GeV

  8. Search for WHWWW* (2 like-sign leptons) Low BR, but channel important in the “intermediate region” 125-145 GeV • Event preselection: • Same charge di-lepton from W’s (one from HWW, the other from prompt W) • Suppress SM backgrounds pT (lepton)> 15 GeV, |h| < 1.1/2.0

  9. Final Selection for WWW* Topological Likelihood discriminant, built on 3 variables per channel

  10. Exclusion limit for WWW* Events after Topological Likelihood discriminant Effect on global combination significant in the intermediate region (125-145 GeV) Being improved in p17 with ZHZWW and also with HZZ*

  11. Combined Higgs boson Search @ DØ New channel With low statistics (0.3 fb-1), the cross-section factors Data/SM = ~ 15 at 115 GeV ~ 9 at 160 GeV With higs statistics (1 fb-1) Data/SM = ~ 5 at 160 GeV Based on our first experiences with Data, can cdf+dØ reach exclusion for a 115 GeV Higgs with 2 fb-1 of data, as early simulation studies were expecting ?

  12. Expected Improvements @ DØ • New b-tagging tool at DØ (bh) • Combines various variables from the track based b-tagging tools in a Neural Network, trained on Monte Carlo • Performance measured on data • Substantial improvement in performance over constituent input b-taggers • Increase of 33% in efficiency for a fixed fake rate of 0.5 % • Jet energy resolution (recalibration + track-jet algorithm) Subtract expected energy deposition in cal Add the track momentum Add the energy of out-of-cone tracks Improve the jet energy resolution by ~20% • Use improved calorimeter calibration Z bb to calibrate b-jet response • L1-cal Trigger (DØ Upgrade) • Important for difficult channels  efficiency improvement (ZHnnbb, hbb) • Addition of SMT Layer 0 (DØ Upgrade) • r@L1 = 2.7 cm  r@L0 = 1.6 cm  better impact parameter resolution • redundancy in pattern recongnition for higher luminosity reduce fake track • Keep performance if degradation of Layer 1 due to radiation damage  further b-tag improvement (~15%)  improvement on Higgs sensitivity

  13. Sensitivity Prospects extrapolated from 0.3 fb-1 results On the Horizon • Will 6 times more lumi take our x-section factors at 115/160 GeV of ~15/9 down to 1?? Maybe.. with analyses improvements under work in CDF and DØ Close ! Equiv Lumi gain (@115) Xsec FactorXsec Factor Ingredients (DØ) mH=115 GeVmH= 160 GeV Today with ~330 pb-1 - 15 9 6.0 6.13.7 Lumi = 2.0 fb-1 NN b-Tagger/L0 3.0 3.5 NN analysis selections 1.7 2.72.8 Dijet-mass resolution 1.5 2.2 Increased Acceptance 1.2 2.02.5 New channels 1.2 1.92.1 Reduced Systematics 1.2 1.7 1.21.5 Combine DØ and CDF 2.0 (assuming similar improvements at DØ and CDF) • At 115 GeV needs ~3 fb-1 • At 160 GeV needs ~5 fb-1  95% CL exclusion for mH= 115-185 GeV with 8 fb-1

  14. Combining Higgs boson Searches Combination Procedure CDF uses a Bayesian approach DØ uses the CLs (LEP) Method the CLS confidence interval is a normalization of CLS+B CLS+B = signal + bkgd hypothesis, CLB = bkgd only hypothesis CLS = CLS+B/CLB : CLS+B & CLB are defined using a “test statistic” Test statistic used is the Log-Likelihood Ratio (LLR=-2 ln Q) generated via Poisson statistics(Q=e-(s+b)(s+b)d/e-bbd) s,b,d=sig.,bkd,data) Tevatron Higgs combination is done with both methods  they give results compatible within 10%.

  15. Tevatron SM Higgs Combination All CDF and DØ results now combined for the first time  mH Limit/SM (GeV)Exp. Obs. 115 7.610.4 130 10.1 10.6 160 5.03.9 180 7.5 5.8 Note: the combined result is essentially equivalent to one experiment with 1.3 fb-1, since both experiments have “complementary” statistics at low and high mass  we are indeed already close to the sensitivity required to exclude or “evidence” the higgs at the Tevatron

  16. Low mass, use Z  bb 4.4 sigma evidence based on about 300 pb-1 of data, shown at ICHEP. Rate consistent with SM production. After double b-tag and “shift” correction MC: 83.3 GeV 13.0 GeV

  17. SUSY Higgs New channels released at ICHEP: bh  b tau tau (3 evts vs 6.3 +- 0.6) Need to combine with bbb and htautau Note: p17 available or close for these channels btautau also getting prepared H+ started, to be done with top group

  18. Manpower Issues Team work to provide best combination, we are strengthening p17 teams and form p20 teams. Enquiry sent around to the group, to find out about new students: 12 institutions have answered with new students there won’t be one topic per student, rather teams of 1-3 student+1-2 postdoc per channel, and use different timescale (2 milestones per years). SM Channels: WH, ZH (nunu), ZH (l+l-), WW, WWW, tau-channels. SUSY Channels: h tautau, bbb, btautau, H+ direct, H+ indirect. BMSSM “higgs” H++, TC, ….

  19. Summary Conclusions • First time with essentially complete result All channels have been analyzed with ~0.3-1 fb-1 of data • Full impact of systematics uncertainties is included • Analyses are steadily improving due to optimization, already close to the Prospective reports Combined limit looks very promising Our outlook for the future looks very interesting • LHC experiments will have to work hard to get the signal before Tevatron, if the Higgs is light (<130 GeV) • But the Tevatron has insight also if it is close to 160 GeV and can exclude at 95%CL from 115 to 185 GeV. • Barring accidents, the Tevatron could have evidence by 2009-2010, if it’s there… But we need to be fast and clever in analyzing  more efforts are needed, input of seniors is welcome !! Besides all analyzers, I would like to thank Suyong and Kazu for excellent collaboration, and welcome Sasha Khanov

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