Recent Results From G. Watts (University of Washington) For the DØ Collaboration QCDElectroWeak TopHiggs

2 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Searches for physics beyond the SM Second Half of New Spring Results Presentation Completing the SM  (WH  Wbb),  (Wbb)  (Zb)/  (Zj),  (H  WW*), Single Top Precision Tests of the SM d  /dp T, d  /dM jj, Azimuthal Jet Decorrelations,  (tt)  (W  ),  (H  ),  (hbb) New Phenomena and B Physics – see talk by A. Nomerotski on March 26 th …

3 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Winter Conference Dataset Thanks to all for the data! All Data Reprocessed by December 2003 with improved reconstruction ~170 pb -1 for these analyses

4 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 W  Cross Section Trilinear Gauge Couplings e channel: pb -1  channel 82.0 pb -1 e channel: pb -1  channel 82.0 pb -1 Small in SM Sensitive to new Physics W p T and M W  Signature e or  and and photon Primary Background W+Jets, jet fakes a .

5 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 W  Backgrounds W+Jets Jet fakes a photon Determine photon fake rate from data 0.3% % for 10 GeV to 50 GeV jets Use sample of events with good electron and apply tracking efficiency. e  W+Jets80.0 ± ± 10 leX3.7 ± ± 0.6 ZZ -4.7 ± 2.0 W    3.4 ± ± 0.3 Total87.1 ± ± 10 Expected Background Event Counts leX Lepton + electron with out track + missing E T tt, etc. Z ,  ’s MC based

6 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 W  Results With increased data detailed W  kinematic studies will be possible Signal Eff calculated using Baur MC + Pythia W  e W  Background Expected 87.1 ± ± 10 Observed14677  (pp  W  l  +X) 19.3 ± 6.7 ± 1.2(lumi) First Step…

7 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 QCD Inclusive Jet and Dijet Cross Sections Run 2 Datasets Better discrimination of PDFs Traditional place to search for new physics Quark Compositeness, etc. Reliable Test of NLO Perturbative QCD Jet Evolution, Parton Distribution Functions, new physics at  s. Look at both Forward and Central Regions Central Region – large transverse energy – most sensitive to new physics and PDFs Forward Region – Less sensitive to new physics, but still sensitive to PDFs Jet Energy Scale is largest systematic error

8 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 d  /dp T Similar, with larger errors, for other eta regions Central Far Forward Forward Central Stay tuned for improvements to JES

9 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 M jj

10 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 The “Biggest” QCD Event

11 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Jet Azimuthal Decorrelations Leading Order pQCD Jets are back-to-back 3 jets in pQCD  12 =   12 <   12 is sensitive to jet formation without having to measure 3 rd jet directly!

12 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Jet Azimuthal Decorrelations Look at events with 2 jets Measure  dijet Compare to a LO & NLO MC LO MC 3 jet production has pole as p T 3 -> 0 LO MC 3 jet  dijet > 2  /3 Not compatible with a LO description

13 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Jet Azimuthal Decorrelations ISR rate in MC has strong effect on matching as well. Further tests of MC Model Important for tt, H mass, etc. More data, better JES will continue to improve the power of this measurement.

14 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Non SM H   Z/y ee – (data)  production (MC) QCD w/jets misidentified (data) SM H   Branching Ratio is small, 10 -3, Beyond SM Suppress Higgs Products Fermiphobic or Top Color Higgs BR(H   ) enhanced BackgroundsRequire 2 isolated EM Objects p T >25 GeV

15 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Non SM H   Look for resonance in M  Split the detector by regions according to fake rates DataTotal BKGQCDDYgg CCCC ± ± ± ± 0.6 CCEC ± ± ± ± 0.1 ECEC ± ± ± ± 0.1 None found, so set limits… Systematic Errors Dominated by Luminosity determination And photon fake rate determination

16 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Non SM H   Fermiophobic model from A. G. Akeroyd, Phys Rev. Lett. 368, 89 (1996) (topcolor) M h (GeV) Analysis improvements possible by making use of CPS, etc.

17 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Tagging a B B Impact Parameter (d) Impact Parameter Resolution d/  (d) Vertex Tagging a B Decay Lengh (L xy ) Decay Length Resolution L xy /  (L xy ) Hard Scatter Top, Higgs contain b-quark jets Most backgrounds do not Leptons from B meson Contain a B meson Has finite life time Travels some distance from the vertex before decaying ~ 1mm With charm cascade decay, about 4.2 charged tracks Several algorithms under active development

18 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 CSIP Algorithm Counting Signed Impact Parameter S(IP) = IP/  (IP) Based on Impact Parameter Significance Jet axis Track I.P  Primary vertex 40% Light Quark Fake Rate 0.5% Requirements to tag a jet: - at least 2 tracks with S(IP) > 3 - or at least 3 tracks with S(IP) > 2 Per Taggable Jet Rates Measured in Data!

19 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 JLIP Algorithm Jet Lifetime Impact Parameter Based on Impact Parameter Significance Probability distributions P(Track from PV) Defined for each class of tracks # of SMT Hits, p T, etc. Each jet assigned P(light quark) Light Quark Fake Rate 40% 0.5%

21 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 SVT Algorithm Z axis Secondary Vertex Tagger Reconstruct Vertices using displaced tracks S(L xy ) = L xy /  (L xy ). Cut on Decay Length Significance 40% 0.5%

22 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 B Tagging Performance on signal tt lepton+jets ~ 56% Single Top (s channel) ~ 52% Wbb ~ 52% Wj ~ 0.3% Combining the Taggers Already studied the correlations Working now on making a combination

23 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Higgs Production at Large tan  Low tan , → Standard Model Higgs High tan , → enhanced bbH –Cross section rises like tan 2  Substantial improvements in Theory understanding since Run 1 ~tan  MSSM Use 3 b-tags Backgrounds Include: QCD: bbh, bbjj, bbbb EW/St: Zb, Z, tt Look for excess in di-jet mass window 4 Jet HF MC QCD not well tested: design around its use Use shoulders to calibrate

24 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 CP-odd Higgs Production CP-even Higgs Production

25 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Higgs Production at Large tan  L=130 pb -1 Background shape determined from data Normalization determined by fitting to region ±1  from expected higgs signal Look for Mass Resonance 3 Jets In Event 20, 15, 15 GeV Trigger on 3 jets + ~60% efficiency

26 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Results Set limit using fitted distributions (TLimit) Will be down at 40 with M A =100 at 1.6 fb -1 No analysis improvements taken into account! Search for SUSY Higgs at high tan 

27 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Higgs Decays High Mass Higgs Searches Low Mass Higgs Searches Nominal Mass Reach Spans Two Decay Modes Search strategies are a function of Decay Channel and Production Channel HDECAY M H [GeV/c 2 ] Excluded

28 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Higgs Production No Good at Low Mass Overwhelmed by QCD background Good at High Mass Good at Low Mass ZH, WH Gluon Fusion Associated Production M. Spira; NLO

29 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Wbb, electron channel Same final state as WH –One of background processes Event selection include –Central isolated e  p T > 20 GeV –Missing E T > 25 GeV –≥ two jets: E T > 20 GeV, |  | < evts. in L int =174 pb -1 of data Fair understanding of data Simulations with Alpgen plus Pythia through detailed detector response Cross sections normalized to MCFM NLO calculations

30 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 At least one b-tag At least two b-tags Wbb, B Tagging Fair agreement Observe 8, expect 8.3±2.2 Add a MT window cut for the W ( GeV) Observe 5 events, expect 6.9±1.8  (Wbb) < 20.3 pb Prefer Wbb at 2  Top is principle background!

31 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Wbb, B Tagging Require N J = 2 Observe 2 evts, expect 2.5± GeV Suppress Top Production WbbWc(c)Wjjtt+tOthers 1.4±0.40.3±0.10.1± ±0.20.1±0.03 Require All Three Tagging Algorithms Observe 2 evts, expect 0.3±0.1 Expect 0.6±0.2 from Wbb SM with no Wbb disfavored at 2  level

32 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 WH Limits Source Uncertainty (%) Jet energy scale14 Jet ID7 b-tagging11 Trigger & e ID5 EM scale5 MC simulations15 Total26  (WH)B(H  bb) < 12.4 pb (M H = 115 GeV/c 2 ) For WH limit use mass window. Expect 0.03 WH, 0.54 from SM backgrounds, observe 0 Add mass window cut GeV/c 95% C.L.

33 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Vertex view of 2nd candidate 3 views of high dijet mass (220 GeV) Wbb (WH) candidate dijet mass (48 GeV) E T miss

34 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Z(  ee/  )b Background to ZH production Benchmark for SUSY Higgs production via gb  bh Probes PDF of the b-quark Measure cross section ratio  (Z+b)/  (Z+j) Many uncertainties cancel Measure cross section ratio  (Z+b)/  (Z+j) Many uncertainties cancel Isolated e/m with p T > 15/20 GeV, |  | < 2.5/2.0 Z peak for signal, side bands for bkgd. evaluations Jet ET > 20 GeV, |  | < 2.5 At least one b-tagged jet L=184 (ee), 152 (  ) pb -1 Jet Flavor Content Calculated with MCFM (NLO) b/c Ratio Background QCD and Z/ 

35 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Z(  ee/  )b Clear Indication of Heavy Flavor Good Match to MC QCD and mistag bkgd. estimated from data Zb normalized to data Tag required

36 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 SourceUncertainty (%) Jet tagging16 Jet energy scale11 Bkgd. estimation6  (Z+c)/  (Z+b)3 Total20 J. Campbell, R. K. Ellis, F. Maltoni, S. Willenbrock Theory hep-ph/ R~0.02

37 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 H  WW ( * )  l + l - Event selection include –Isolated e/  p T (e 1 ) > 12 GeV, p T (e 2 ) > 8 GeV p T (e/  1 ) > 12 GeV, p T (e/  2 ) > 8 GeV p T (  1 ) > 20 GeV, p T (  2 ) > 10 GeV –Missing E T greater than 20 GeV (ee, e  ); 30 GeV (  ) –Veto on Z resonance Energetic jets High Mass SM Higgs Search L = 180 (ee), 160 (e  ) and 150 (  ) pb -1  Channel

38 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 H  WW ( * )  l + l - W+W+ e+e+ W-W- e-e- n Higgs of 160 GeV Spin Correlations  (ll) – Azimuthal Angle QCD Z  Leptons from Higgs Tend to be collinear Can’t reconstruct mass due to presence 2 neutrinos WWW+jetsWZtt 2.51 ± ± ± ±0.01

39 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 H  WW ( * )  l + l - Signal acceptance is ~ 0.02 – 0.2 depending on the Higgs mass/final state eeee  Observed225 Expected2.7±0.43.1±0.35.3±0.6 DØ Run II Preliminary Higgs of 160 GeV After all Cuts  X BR 95% CL ee

40 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Top Quark Run 1 World Average Top Mass Run 2 Cross Sections All jets, dilepton, l+jets Precision Measurement in Run 2 Cross Section Cross Check SM with M Top “Rare” Decays Mass Constrain M Higgs Stay tuned for  ’s

41 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Di-Lepton Top Cross Section Small cross section Relatively free of SM backgrounds SM Backgrounds ALPGEN+Pythia Instrumental Fakes Fakes Isolated Lepton Fakes Estimated on data

42 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Cuts ee  ee

43 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Dilepton Cross Section

44 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Dilepton Cross Section Cross section shows some excess which is still consistent with the standard model expectation. We are looking forward to collecting more data!!

45 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Lepton + Jets Fit shapes from likelihood discriminate of signal and background 1 Preselection cuts removes all but W+Jets 2 Determine Topological Variables No B-tagging 3 Create Likelihood Discriminent 4 Fit data to combinations of backgrounds and signal Preselection Cuts include NJets>=4, etc. Systematics Driven Method LP’03 results were close to being systematics driven

46 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Lepton + Jets Topological Variables Good S:B Minimize JES Small Correlations Sphericity Aplanarity H T2 /H Z K Tmin H T2 /H Z Centrality H T of all but leading jet K Tmin K T of #4 jet relative to #3 jet.

47 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Lepton + Jets

48 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Lepton + Jets Total  +Jets e+Jets

49 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 All Jets Cross Section 46% of ttbar production QCD is many orders mag greater Simple Cuts aren’t enough! 6 Jets, exactly one btag Background Rejecting NN Top Hypothesis NN Cut Top Quantity NN NN are trained on data for background, and ttbar MC for signal H T,H 3j T,, sphericity, aplanarity, centrality E T 4,5, average eta  ww,  tt, M WW, M tt, M min 1,2, M min 3,4

50 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Discriminating Variables Variables are designed to address different aspects of the background Energy Scale – H T, sqrt(s) Soft non-leading Jets – H 3j T, E T 5,6, Event Shape – Sphericity, aplanarity Rapidity – Centrality, Top Properties – Top and W Mass Likelihood, M WW, M tt, min dijet masses Background model is data-derived JES Systematics

51 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 All Jets Cross Section events pass all cuts Expect 186 ± 5(stat) ± 7.5(sys) Uncertainty (%) Vertex ID1 Jet ID10 JES28 Jes Resolution0.6 Top Mass7.6 Trigger4 Tagging4.0 Total31

53 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Top Mass Combination DØ New Run I Top Mass Result is now part of the TeV M Top combination (see Juan’s April W&C) Old Combination M t = ± LEP EWWG

54 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Really want to talk about… (Old TeV Top Mass) Squeezing Run 2 Top and W Mass Errors Extensive program in place Coming to a Wine And Cheese near you soon…

55 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 W/Z Cross Sections Analyses in Progress Not updating cross sections this time around, but we have a new sample and new analysis in advanced state of review

56 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Forward Proton Detector D S Q2Q2 Q3Q3 Q4Q4 S A1A1 A2A2 P 1U P 2I P 2O P 1D Z(m) D2 D Veto Q4Q4 Q3Q3 Q2Q mm from 30 m 0.92 < t < 3 GeV GeV Installation is Complete! Analysis in progress dN/dT, diffractive jets

57 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Single Top Single Top Production gives you access to B(t  WB) |V tb | W Helicity Top Polarization Top Width Anomalous couplings Rare Decays Preselect Events Apply BTagging Apply Topological Cuts QCD (fakes) W+Jets ttbar Backgrounds (MC) (Data)  +jets/SVT

58 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Expected Sensitivity SLTSVTJLIPSLTSVT s-channel 0.67      0.35 t-channel 0.95      0.56 tt 9.60      3.75 non-top 31.1      11.8 Total expected 42.4      12.4 Observed Without SystematicsWith Systematics  s (pb) <6.4<13.8  t (pb) <9.0<19.8  s+t (pb) <7.9<15.8 Expected Limit! We have not applied final topological cuts yet! Already better than Run 1 limits! Electron Channel Muon Channel

59 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Conclusions

60 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Conclusions Taking advantage of the Data –QCD program is under way with jet cross sections and studies. –Electro weak is moving to the next level of accuracy –Higgs is demonstrating an understanding of the most important backgrounds –Top has remeasured the cross section. Mass result will appear soon. –Many new analyses and conference results. More in the pipeline! –Write-ups available for all analyses Improvements On Tap –JES –Already have another 70 pb -1 on tape. –New Ideas…

62 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Jet Cone Algorithm

63 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Jet Cone Algorithm

64 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Dilepton Event

65 Gordon Watts (UW Seattle) Fermilab Wine and Cheese 4/9/2004 Multi-jet Background Full Multijet Sample 2-Tagged Sample Calculate TRF (p T & 3 Regions of  ) Apply TRF 3-Tagged Jet Distribution Fit outside to real 3 Tagged Distribution bbbb, zbb Shapes are similar, so fit should take care of them to first order Fitted Background