D0 Higgs Results and Tevatron Higgs Combination

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1 D Higgs Results and Tevatron Higgs Combination Graham W. Wilson University of Kansas July 3rd On behalf of the CDF and D collaborations Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

2 Outline Introduction Higgs Introduction 3 D Higgs Results: Channel by Channel 4 D Higgs Combination 5 Tevatron Higgs Combination 6 Conclusions Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

was essentially the only running high energy collider capable of directly exploring high

3 Tevatron Run II Introduction pp collisions at s=.96 TeV Over years, more than fb recorded per experiment Timeline For past years, the Tevatron was essentially the only running high energy collider capable of directly exploring high energy phenomena. Now only the LHC has this privilege for the near future. Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 3 / 3

4 D Detector Introduction D B=.9T, R =.5m Technically - could have kept going for 3 more years Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 4 / 3

5 Introduction Putting things in context Experiments (direct and indirect) have been constraining the SM Higgs habitable zone for decades As you all know and were very recently reminded, the latest LHC results indicate the presence of a new particle consistent with the Standard Model Higgs boson with a mass near 5 GeV The LHC results together with prior results principally from LEP, SLC and Tevatron constrain the SM Higgs should it exist to a narrow 5 GeV wide mass region near 5 GeV Evidence is strongest in the γγ and 4-leptons (ZZ ) decay modes The Tevatron experiments have been searching for the Higgs for the last decade, and now have close to final results to report which provide an independent and complementary test of this new phenomenon in the - GeV mass range and in particular near 5 GeV Tevatron is sensitive to different decay modes and production mechanisms (for more details see Michelle Stancari s talk) Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 5 / 3

m H = 5 GeV Relative sensitivities (in expected exclusion rate) of some of the channels Channel H WW l

6 D Higgs Searches Higgs Introduction D Higgs Searches Many channels are searched motivated by m H in the - GeV mass range. m H = 5 GeV Relative sensitivities (in expected exclusion rate) of some of the channels Channel H WW l + l E T 3.6 ZH ννbb 3.9 WH lνbb 4. ZH l + l bb 5. R exp 95 Channel H γγ 8. 3 l (WH, ZH). e ± µ ± (WH).6 ττ.8 R exp 95 Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 6 / 3

7 Higgs Introduction Quantifying Evidence For/Against a Signal Hypotheses SM Higgs search involves testing two hypotheses H b (Null) : Only SM background events H s+b (Signal) : Presence of SM Higgs and SM background events Likelihood Ratio Form a (log) likelihood ratio test-statistic to compare the two hypotheses LLR obs LLR = log p(data H s+b) p(data H b ) Define CL s CL s+b /CL b where CL s+b = p(llr LLR obs H s+b ) CL b = p(llr LLR obs H b ) S+B Pseudo- Experiments B-Only Pseudo- Experiments Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 7 / 3

8 Higgs Introduction What To Expect With Log-Likelihood Ratio S+B Pseudo- Experiments LLR obs B-Only Pseudo- Experiments LLR Distribution Pseudo-experiments with H b true Pseudo-experiments with H s+b true Example observed value of LLR obs Log Likelihood Ratio 5 Tevatron RunII Preliminary LLR b ± s.d. 4 LLR b ± s.d. m H =5 Signal Injection LLR b 3 Rate =. SM LLR s+b LLR obs June Expectations Dashed black and red lines show median LLR values expected under both hypotheses vs m H Sensitivity greatest when these two lines are most separated Black curve: median expected outcome if 5 GeV SM Higgs present Mass resolution -5 GeV - so the median LLR obs differs from median LLR b for a range of m H hypotheses Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 8 / 3

9 D Higgs Results: Channel by Channel H WW l + l E T (l i = e or µ) Event Selections Selections for ee, µµ and eµ Main backgrounds DY and WW Overview: preselection, DY rejection, BDT final discriminants Separate in -jet, -jet, -jet bins e µ channel has best signal ( ) and lowest background Plots from eµ selection Events/4 GeV 4 DO Preliminary data L = 9.7 fb 3 eµ + MET Z+jets Diboson Events/. Events/. DO Preliminary L = 9.7 fb eµ + MET Final Discriminant DO Preliminary L = 9.7 fb eµ + MET data Z+jets Diboson W+jets Multijet ttbar Sig Tot M H = 5 GeV data Z+jets Diboson W+jets Multijet W+jets ttbar Multijet Sig Tot ttbar min M T (GeV) Signal (M = 65 GeV) H Final Discriminant M H = 65 GeV Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 9 / 3

10 D Higgs Results: Channel by Channel H WW l + l E T (l i = e or µ) Upper Limits 95% CL Limit/SM DØ Preliminary L = 9.7 fb (b) eµ + E T 95% CL Limit/SM DØ Preliminary L = 9.7 fb (c) ee + E T Standard Model =. Standard Model = M H (GeV) M H (GeV) 95% CL Limit/SM DØ Preliminary L = 9.7 fb (d) µµ + E T 95% CL Limit/SM DØ Preliminary L = 9.7 fb (a) ll + E T Observed Limit Expected Limit Expected s.d. Expected s.d. Standard Model =. Standard Model = M H (GeV) 95% CL upper limit: 4.6 (3.6) σ SM observed (expected) at 5 GeV M H (GeV) Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

11 D Higgs Results: Channel by Channel ZH ννbb Channel Event Selection Pair of b-jets + E T Designed for ZH. Also sensitive to WH where l from W unidentified Backgrounds: V + heavy-flavor jets, top quarks, multi-jet (MJ) Control samples for background modeling (lepton+jets and MJ) Use B-tagging and MVAs. Validate with analysis of VZ Events / D Preliminary (9.5 fb ) Data Top V+h.f.+VV V+l.f. Multijet VH(5) 5 ZH ννbb Analysis sample (Pre b tag) E T Significance Events /. Events /. ZH ννbb Analysis sample (Medium b tag) 7 MJDT >.3 D Preliminary (9.5 fb ) Final Discriminant Data Top V+h.f.+VV V+l.f. Multijet VH(5) ZH ννbb Analysis sample (Tight b tag) MJDT >.3 D Preliminary (9.5 fb ) Final Discriminant Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3 Data Top V+h.f.+VV V+l.f. Multijet VH(5)

12 D Higgs Results: Channel by Channel ZH ννbb Channel Limits Events /. Limit / σ(pp (W/Z)H) BR(H bb) 3 ZH ννbb Analysis sample (Tight b tag) D Preliminary (9.5 fb ) Background only Fit Data Bkgd VH(5) +/ σ Final Disciminant Observed Limit Expected Limit Expected ± Expected ± s.d. s.d. D Preliminary (9.5 fb ) m H (GeV) 4.3 (3.9) σ SM observed (expected) at 5 GeV D Preliminary (9.5 fb ) S+B Fit Data VZ 8 Top 6 V+h.f.+WW 4 V+l.f. Multijet DiJet Invariant Mass Events / 8. Events / D Preliminary (9.5 fb ) S+B Fit VZ Analysis sample (Tight b tag) VZ Analysis sample (Tight b tag) Data Bkgd VZ +/ σ DiJet Invariant Mass Measure WZ+ZZ cross-section.94 ±.3 ±.34 times expectation Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

13 D Higgs Results: Channel by Channel WH lνbb Channel Event Selection Events /Bin l + -jets ( b-tagged) + E T T-ST, (L,M,T)-DT b-tag categories Backgrounds: V + heavy-flavor jets, top quarks,3,4-jet categories V( lν)+ jets, Tight Single Tag 8 DØ Preliminary, 9.7 fb 6 Data 4 Multijet V+lf V+hf tt single t 8 VV M =5 GeV 6 H ( ) Dijet Mass (GeV) Events / Bin Events /Bin V( lν)+ jets, Pre Tag DØ Preliminary, L=9.7 fb Data Multijet V+lf V+hf tt single t VV M H =5 GeV ( ) Dijet mass (GeV) V( lν)+ jets, Tight Double Tag DØ Preliminary, 9.7 fb Data Multijet V+lf V+hf tt single t VV M H=5 GeV ( ) Dijet Mass (GeV) Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 3 / 3

14 D Higgs Results: Channel by Channel WH lνbb Channel Limits Events /Bin Events V( lν)+ jets, Tight Double Tag DØ Preliminary, 9.7 fb Final Discriminant 5 5 Data Multijet V+lf V+hf tt single t VV M H=5 GeV ( ) DØ Preliminary, L=9.7 fb 5 DØ Data Background SM Higgs Signal ± s.d. on Background 5 (SM Higgs 4) MVA Output June LLR 95% CL Limit / SM 6 4 DØ Preliminary, 9.7 fb LLR B σ LLR B σ LLR B LLR S+B LLR obs m H (GeV) DØ Preliminary, 9.7 fb Observed Limit Expected Limit Expected Limit ± σ Expected Limit ± σ Standard Model = M H (GeV) 95% CL limit of 4.5 σ SM observed cf 4. σ SM expected at 5 GeV Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 4 / 3

15 D Higgs Results: Channel by Channel ZH llbb Channel Event Selection Events -leptons + -jets ( b-tagged) Constrain ll to m Z and llbb p T Backgrounds: Z + heavy-flavor jets, top quarks Use tt MVA to split in tt-depleted and tt-rich subsamples Double Tag DØ Preliminary, 9.7 fb Data Z+LF Z+bb Z+cc Top Diboson Multijet ZH x tt RF Output Signal samples with m H = 5 GeV Events Events Pretag DØ Preliminary, 9.7 fb Data Z+LF Z+bb Z+cc Top Diboson Multijet ZH x Dijet mass [GeV] Double Tag, tt RF >.5 DØ Preliminary, 9.7 fb 3 Data Z+LF 5 Z+bb Z+cc Top Diboson Multijet 5 ZH x Dijet mass (Kinematic Fit) [GeV] Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 5 / 3

16 D Higgs Results: Channel by Channel ZH llbb Channel Limits Events Double Tag, tt RF> Data Z+LF Z+bb Z+cc Top Diboson Multijet LLR 4 3 DØ Preliminary, 9.7 fb ZH ll bb LLR B σ LLR B σ LLR B LLR S+B LLR OBS 4 Background Fit DØ Preliminary, 9.7 fb 3 Events RF Output Double Tag, tt RF>.5 Data Bkgd Signal 5 Bkgd ± σ Limit / σ(pp ZH) BR(H bb) M (GeV/c ) H DØ Preliminary, 9.7 fb Observed Limit Expected Limit Expected ± Expected ± s.d. s.d. ZH ll bb Background Fit DØ Preliminary, 9.7 fb RF Output M (GeV/c ) H 95% CL limit of 7. σ SM observed cf 5. σ SM expected at 5 GeV Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 6 / 3

17 D Higgs Results: Channel by Channel Inclusive H γγ Channel Event Selection photons with E T > 5 GeV Identify photons from jet fakes Measure backgrounds from γγ, γ-jet, jet-jet Use separate kinematic BDT for photon and jet-dominated samples Events per.5 GeV bin DØ preliminary, 9.7 fb Data γγ γ+jet jet+jet Z/γ* ee signal(m =5 GeV)x5 H M γγ (GeV) Events per.8 bin DØ preliminary, 9.7 fb 5 Data γγ 4 γ+jet 3 jet+jet Z/ γ* ee signalx (M =5 GeV) BDT output H 95% C.L. limit/sm 5 DØ preliminary, 9.7 fb Observed Expected Expected ± s.d. Expected ± s.d M H (GeV).6 (8.) σ SM observed (expected) at 5 GeV Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 7 / 3

18 D Higgs Results: Channel by Channel Trileptons Channel. WH, ZH, H. Leading to lllx Event Selection 95% CL Limits / σ SM Mainly for WH, ZH with H VV Focus on eeµ, µµe channels Backgrounds: WZ, ZZ, Z+jets, Z γ Use BDTs to exploit signal characteristics (3 in µµe channel) - D Preliminary, L=9.7 fb VH VWW eeµ,µµe Standard Model =. Observed Limit Expected Limit Expected ±σ Expected ±σ m H (GeV/c ) 9.3 (.) σ SM observed 5 GeV Entries Entries D Preliminary L = 9.7 fb eeµ+e T Final BDT Discriminant D Preliminary L = 9.7 fb µµe+e T significance Z + E T > Final BDT Discriminant data Diboson Z+jets W+jets ttbar Signal m H =45 GeV data Zγ Diboson Z+jets W+jets ttbar Signal 5 m H =45 GeV Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 8 / 3

19 D Higgs Results: Channel by Channel D Channel Summary Results for m H = 5 GeV All main channels find signal-like excesses in data for m H = 5 GeV. No individual channel by itself shows high significance. Channel R exp 95 R obs 95 H WW l + l E T ZH ννbb WH lνbb ZH l + l bb H γγ l (WH, ZH). 9.3 e ± µ ± (WH) ττ Total.7.94 Next: D combination plots for all Higgs masses. Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 9 / 3

20 D Higgs Combination D Higgs Combination Log Likelihood Ratio 5 DØ Preliminary, L 9.7 fb LLR b ± s.d. int SM Higgs Combination LLR b ± s.d. LLR b LLR s+b 5 LLR obs 5 D Result Data is more consistent with the expected signal hypothesis for SM Higgs masses in the -4 GeV range than the background-only hypothesis Log Likelihood Ratio June Observed LLR Signal Injected LLR m H =5 GeV,.xSM rate Signal Injected LLR m H =5 GeV,.5xSM rate DØ RunII Preliminary L int 9.7 fb Signal Injection Test Add m H = 5 GeV signal events with SM Higgs cross-section and BRs Blue curve shows median expected outcome if a SM Higgs of 5 GeV is present Purple curve shows median expected outcome if a SM-like Higgs of 5 GeV is present with.5 times SM rate June Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

21 D Higgs Combination Hypothesis Test Results (Focussing on Low Mass) Background p value CL s+b 3 DØ Preliminary, L 9.7 fb int SM Higgs Combination CL b Observed CL b Expected Expected ± s.d. Expected ± s.d June DØ Preliminary, L 9.7 fb int SM Higgs Combination CL s+b Observed CL s+b Expected Expected ± s.d. Expected ± s.d. σ σ 3σ σ σ Inconsistent with Background Hypothesis Black: Probability for B to fluctuate up to as signal-like or more an observed outcome Background p-value = 4% for m H = 5 GeV Dashed: Median expected B p-value if S+B hypothesis true Consistent with Signal Hypothesis Black: - probability for S+B to fluctuate up to as signal-like or more an observed outcome Dashed: Median expected CL s+b if B is true 3 3σ June Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

22 D Higgs Combination Mass Limits and Signal Strength CL s Best Fit σ / σ SM DØ Preliminary, L 9.7 fb int SM Higgs Combination 95% C.L. CL s Observed CL s Expected Expected ± s.d. Expected ± s.d June 3.5 DØ Preliminary, L 9.7 fb int SM Higgs Combination Best Fit ± s.d June Exclusion Strength Black: D Data exclude SM Higgs with masses from 59-7 GeV at at least 95% CL In the 5-45 GeV region, the data favor the signal hypothesis Signal Strength Best fit signal strength (with ±σ uncertainty band) Consistent with SM Higgs at low mass Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd / 3

23 D Higgs Combination Decays to bb. Decays to WW Log Likelihood Ratio 4 DØ Preliminary, L 9.7 fb LLR b ± s.d. int LLR b ± s.d. SM H bb Combination LLR b LLR s+b 8 LLR obs June σ / σ SM 95% CL Limit on DØ Preliminary, L int 9.7 fb SM H bb Combination Observed Expected w/o Higgs Expected ± s.d. Expected ± s.d. Log Likelihood Ratio 5 DØ Preliminary, L 9.7 fb LLR b ± s.d. int SM H WW Combination LLR b ± s.d. LLR b LLR s+b 5 LLR obs June σ / σ SM 95% CL Limit on DØ Preliminary, L 9.7 fb int SM H WW Combination Observed Expected w/o Higgs Expected ± s.d. Expected ± s.d June June Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 3 / 3

24 D Summary Plot D Higgs Combination σ / σ SM 95% CL Limit on DØ Preliminary, L 9.7 fb int SM Higgs Combination LEP Exclusion DØ Exclusion Observed Expected w/o Higgs Expected ± s.d. Expected ± s.d June D data does not exclude a SM Higgs with mass near 5 GeV (expected 95% CL limit =.7 σ SM for B-hypothesis). Overall background-only p-value = 4% Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 4 / 3

25 Tevatron Higgs Combination Log-Likelihood Ratio Log Likelihood Ratio 4 Tevatron RunII Preliminary LLR b ± s.d. 3 LLR b ± s.d. SM Higgs, L. fb int LLR b LLR s+b LLR obs Tevatron Result Data is much more consistent with the expected signal hypothesis for SM Higgs masses in the -4 GeV range than the background-only hypothesis Log Likelihood Ratio June 5 Tevatron RunII Preliminary LLR b ± s.d. 4 LLR b ± s.d. m H =5 Signal Injection LLR b 3 Rate =. SM LLR s+b LLR obs Signal Injection Test Add m H = 5 GeV signal events with SM Higgs cross-section and BRs Solid black curve shows median expected outcome if a SM Higgs of 5 GeV is present Mass resolution typically -5 GeV - so the median LLR obs differs significantly from the median LLR b for a range of m H hypotheses June Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 5 / 3

26 Tevatron Higgs Combination Hypothesis Test Results (Focussing on Low Mass) Background p value CL s+b 3 4 Tevatron RunII Preliminary L. fb CL b Observed CL b Expected Expected ± s.d. Expected ± s.d June 3 4 Tevatron RunII Preliminary L. fb CL s+b Observed CL s+b Expected Expected ± s.d. Expected ± s.d. σ σ 3σ 4σ σ σ 3σ Inconsistent with Background Hypothesis Black: Probability for B to fluctuate up to as signal-like or more an observed outcome Background p-value =.4% for m H = 5 GeV Dashed: Median expected B p-value if S+B hypothesis true Consistent with Signal Hypothesis Black: - probability for S+B to fluctuate up to as signal-like or more an observed outcome Dashed: Median expected CL s+b if B is true 4σ June Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 6 / 3

27 Tevatron Higgs Combination Mass Limits and Signal Strength CL s Tevatron RunII Preliminary L. fb 95% C.L. CL s Observed CL s Expected Expected ± s.d. Expected ± s.d June Best fit σ/sm Tevatron Run II Preliminary, L. fb - June SM= m H (GeV/c ) Exclusion Strength Black: Data exclude SM Higgs with masses in the ranges -3 and 47-8 GeV at at least 95% CL In the -4 GeV region, where there is sensitivity to exclude at around 95% CL, the signal-like excess in the data precludes setting useful limits Signal Strength Best fit signal strength (with ±σ uncertainty band) Consistent with SM Higgs (5-4 GeV) Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 7 / 3

28 Tevatron Higgs Combination Decays to bb. Decays to WW. Decays to γγ Background p value Tevatron RunII Preliminary SM H bb, L. fb CL b Observed CL b Expected Expected ± s.d. Expected ± s.d. σ 95% CL Limit/SM Tevatron Run II Preliminary H WW, L. fb - Observed Expected w/o Higgs ± s.d. Expected ± s.d. Expected σ SM= June (σ WH +σ ZH ) x Br(H bb ) (fb) Tevatron Run II Preliminary H bb, L. fb - Measured 68% C.L. 95% C.L. Predicted 3σ June m H (GeV/c ) 95% CL Limit/SM Tevatron Run II Preliminary H γγ, L. fb - Observed Expected w/o Higgs ± s.d. Expected ± s.d. Expected June m H (GeV/c ) SM= June m H (GeV/c ) Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 8 / 3

29 Summary Plot Tevatron Higgs Combination 95% CL Limit/SM Tevatron + LEP Exclusion LEP Exclusion LEP+ATLAS Exclusion Tevatron Run II Preliminary, L. fb - ATLAS Exclusion ATLAS Exclusion Observed Expected w/o Higgs ± s.d. Expected ± s.d. Expected Tevatron +ATLAS+CMS Exclusion ATLAS+CMS Exclusion + H W W H γγ Tevatron Run II Preliminary L. fb m H = 5 GeV/c Combined (68%) Single Channel SM= H bb CMS Exclusion ATLAS+CMS Exclusion June m H (GeV/c ) Tevatron data does not exclude a SM Higgs with mass near 5 GeV (expected 95% CL limit =.8 σ SM for B-hypothesis) June Best Fit σ/σ SM Data is consistent with expected decay modes of 5 GeV SM Higgs including decay to bb. Overall background-only p-value =.4%. Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 9 / 3

30 Concluding Remarks Conclusions Summary The RunII era of the Tevatron experiments data-taking is over Close to final results from D indicate an excess of events at low-mass more consistent with SM Higgs hypothesis than background-only - with contributing indications in several channels Background fluctuation probability for m H = 5 GeV is 4% for D. Combined results from Tevatron and CDF have.4% overall background fluctuation probability for m H = 5 GeV Breakdown by channel is consistent with Standard Model Higgs In particular the data are consistent with a significant Higgs coupling to bb as expected if the Higgs is also responsible for fermion mass generation Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 3 / 3

31 Backup Slides Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 3 / 3

32 Tevatron combined bb limit Tevatron Run II Preliminary H bb, L. fb - 95% CL Limit/SM Observed Expected w/o Higgs ± s.d. Expected ± s.d. Expected SM= June m H (GeV/c ) Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 3 / 3

33 Higgs Couplings Predicted in SM - but only starting to be explored. Graham W. Wilson (University of Kansas) BEACH, Wichita July 3rd 33 / 3

Measurements of Fermionic Couplings of the Standard Model Higgs Boson using the bb, ττ and µµ Decay Channels with the ATLAS Detector

Measurements of Fermionic Couplings of the Standard Model Higgs Boson using the bb, ττ and µµ Decay Channels with the ATLAS Detector International Europhysics Conference on High Energy Physics Venice,