ICHEP 2004, August 16-22, Beijing China Dmitri Denisov, Fermilab Results for Top and Higgs at Tevatron Results for Top and Higgs at Tevatron Tevatron Ø CDF and DØ Top quark studies Search for Higgs Summary Outline

Dmitri Denisov, ICHEP04, August Top Quark Studies and Higgs Searches Discovery of top quark at Fermilab in 1995  Completed SM Quark Sector Studies of heaviest known elementary particle  SM parameters, tests  Beyond SM searches Higgs boson is last missing particle in SM  Describes EWSM – particle masses Experimental challenges: low cross sections and substantial backgrounds  Accelerator  Detectors  Analysis Tevatron currently is the only accelerator able to produce such heavy particles

Dmitri Denisov, ICHEP04, August Tevatron Parameters Interactions/ crossing Bunch crossing (ns)  Ldt (pb -1 /week) 3    Typical L (cm -2 s -1 )  s (TeV) 36  36 6  6 Bunches in Turn Run IIbRun IIaRun I Run I  Run IIa  Run IIb 0.1 fb -1 Substantial upgrades for Run II:  10% energy increase: 30% higher  top  integrated luminosity increase: x50 6 km long Tevatron ring

Dmitri Denisov, ICHEP04, August Tevatron Run II Performance Peak luminosity is above cm -2 sec -1 Reliable operation  in stores ~120 hours/week Total ~0.7 fb -1 delivered in Run II  as planned cm -2 sec -1 1 week=168 hours 0.7 fb -1

Dmitri Denisov, ICHEP04, August Tevatron Long Term Luminosity Plan To reach higher masses with the same energy  higher luminosity Increase in number of antiprotons  the key for higher luminosity Expected peak luminosity  cm -2 sec -1 by 2007 Currently expecting delivered luminosity to each experiment  4-8 fb -1 by the end of 2009 Today

Dmitri Denisov, ICHEP04, August CDF and DØ Experiments in Run II New Silicon Detector New Central Drift Chamber New End Plug Calorimetry Extended muon coverage New electronics Silicon Detector 2 T solenoid and central fiber tracker Substantially upgraded muon system New electronics Driven by physics goals detectors are becoming “similar”: silicon, central magnetic field, hermetic calorimetry and muon systems CDF ØDØØDØ

Dmitri Denisov, ICHEP04, August Data Collection by Experiments CDF and D0 experiments are very complex Typical ratio of “recorded” to “delivered” luminosity is 80%-90% As of now both experiments recorded ~0.5 fb -1 Results presented correspond to ~0.2 fb -1 Analyzed data

Dmitri Denisov, ICHEP04, August Detection of High P t Objects Electrons Missing E t Muons Jets D0 Preliminary Top and Higgs final decay products  electrons  muons  jets (b)  missing E t ( ) Detection and MC optimization using well known objects b tagging

Dmitri Denisov, ICHEP04, August Top Quark Studies Heaviest known elementary particle: 180GeV  measure properties of least known quark  top quark mass constrains Higgs mass  sensitive to new physics  short life time: probe bare quark

Dmitri Denisov, ICHEP04, August Top Quark Production and Decays Top quarks at Tevatron are (mainly) produced in pairs via strong interaction Top pair cross section at 1.96 TeV is 6.7 pb In SM top decays 100% to Wb Classification of top decays is based on W s decays % e qq e   qq44.4 Top decays classification: di-lepton, lepton+jets, all jets Production Decay 85% 15%

Dmitri Denisov, ICHEP04, August Selection of Top Quark Events In triggering and analysis select events with  high P t leptons  high E t multiple jets  large missing E t ( )  displaced vertex for b jets “ Di-lepton” mode has  low backgrounds: di-bosons, Drell-Yan,...  but low statistics: ~5% for e,  decays “Lepton+jets” very productive mode  6 times more decays then di-lepton mode  main background W+jets  good purity after b tagging “All jets” mode  ~50% branching  high QCD backgrounds, jets combinatoric

Dmitri Denisov, ICHEP04, August DØ Top Cross Section in di-lepton Channel Topological selection  isolated (not in jet) high P t ee(156 pb -1 ),  (140 pb -1 ), e  (143 pb -1 ) pair  2 or more jets  large missing E t Backgrounds: WW, Z+jets, W+jets, fakes Extra b tag Ultra-pure sample of top events: S/N>50 e  only D0 Run II Preliminary Cross Section

Dmitri Denisov, ICHEP04, August CDF Top Cross Section in di-lepton Channel 197 pb -1 data sample for all channels  topological selection Combine ee,  and e  channels for best precision pb

Dmitri Denisov, ICHEP04, August CDF Top Cross Section in lepton+jets Channel l+jets with vertex b tagging l+jets with soft lepton tagging l+jets topological Exploit different strategies  higher statistics – topological  b-jets tagging  displaced vertex  soft lepton (  )

Dmitri Denisov, ICHEP04, August DØ Top Cross Section in lepton+jets Channel Selection of events (topological method)  high P t lepton  large missing E t  4 or more jets (no b tagging) Form topological discriminant to optimize top events selection Single b tagDouble b tag Tagging jets from b decays using displaced vertex algorithms reduces backgrounds substantially

Dmitri Denisov, ICHEP04, August Run II Top Quark Cross Section: Summary Measurements demonstrate success of multiple top detection techniques Results within errors consistent with NNLO SM predictions for 1.96TeV of 6.7pb Errors between different channels are correlated

Dmitri Denisov, ICHEP04, August Top Quark Mass Measurement Fundamental SM parameter Top mass together with EW data constrain Higgs mass Ø Using Run I l+jets events (125 pb -1 ) DØ developed “matrix element method” Detailed knowledge of top quark decay and detector response is required  event by event likelihood calculated vs m t m t =  3.6(stat)  3.9(syst) GeV PDFs Phase space x LO MEProbability for observable x when y was produced (Ex: quark E T  jet E T ) Currently single most precise top mass measurement

Dmitri Denisov, ICHEP04, August Run II Top Mass Measurement at CDF Run I style “template” method is efficiently used di-leptonsl+jets, b tagged l+jets, multivariate Dynamical Likelihood Method is similar to D0 “matrix element method” Single most precise Run II measurement

Dmitri Denisov, ICHEP04, August Top Quark Mass Measurement at DØ in Run II Measurements in l+jets channel (~150 pb -1 )  template method uses templates for signal and background mass spectra  ideogram method uses analytical likelihood for event to be signal or background Template method m t = 170  6.5(stat)+10.2/-5.7(syst) GeV Ideogram method m t =  5.8(stat)  7.1(syst) GeV Template Ideogram

Dmitri Denisov, ICHEP04, August Tevatron Top Quark Mass Measurement New combined Run I result  (Was m t =  5.1 GeV) m t =  4.3 GeV Run II top quark mass results from both detectors are available Ø TeV EWWG is working on combining Run II top mass measurement from CDF and DØ Systematic error (mainly jet energy scale) is becoming limiting accuracy factor

Dmitri Denisov, ICHEP04, August Search for Single Top Quark Production EW production of top quark  direct probe of |V tb |  search for new physics Events selection: is similar to top pairs in l+jets mode, but with lower jets multiplicity  backgrounds (W+jets, tt, di-bosons) are substantial 95% C.L. limitsCDFDØDØ  s-channel) <13.6pb<19pb  t-channel) <10.1pb<25pb  s+t channels) <17.8pb<23pb Need above 1 fb -1 for observation

Dmitri Denisov, ICHEP04, August Unexpected Top Quark Decay Modes? Assuming three-generation CKM matrix unitarity, |V tb |~1.0 R = BR(t  Wb)/BR(t  Wq) ~1.0 Can measure ratio by checking the b quark content of the top sample decay products If efficiency to tag a b quark is  b (~0.45 at CDF), then  2 =(b  b ) 2  1 =2b  b (1-b  b )  0 =(1-b  b ) 2 “double tag” “single tag” “no tag” BR(t  Wb)/BR(t  Wq) >0.62 at 95% C.L. Does top decays into something besides SM Wb?  Like Xb, where X  qq (100%) or Yb, where Y  l  (100%)? Estimate branching limits using ratio of top cross sections  ll /  lj Br(t  Xb) <0.46 at 95% C.L. Br(t  Yb) <0.47 at 95% C.L. (CDF) R(  b -  light )

Dmitri Denisov, ICHEP04, August Is Top to Wb vertex SM? W Helicity Test of V-A coupling in top decays: in SM W couples only to LH particles This together with angular momentum conservation allows top to decay into LH (negative helicity) or longitudinally-polarized (0 helicity) W bosons In SM F - =0.30, F 0 =0.70, F + =0 Helicity of W manifests itself in decay product kinematics CDF (l+jets and di-lepton) Ø DØ (l+jets, 160 pb -1 ) No deviations from SM predictions F + < 0.24 at 90% C.L. topological F + < 0.24 at 90% C.L. b tagging

Dmitri Denisov, ICHEP04, August Experimental Limits on Higgs Mass Available experimental limits  direct searches at LEP M H >114 GeV at 95% C.L.  precision EW fits Light Higgs favored at 95% C.L. Tevatron provides: Precision m t and M w measurements Direct searches  SM Higgs  non-SM Higgs LEP

Dmitri Denisov, ICHEP04, August SM Higgs Production and Decays at Tevatron Production Decays Production cross section  in the 1 pb range for gg  H  in the 0.1 pb range for associated vector boson production Decays  bb for M H < 130 GeV  WW for M H > 130 GeV Search strategy: M H <130 GeV associated production and bb decay W(Z)H  l (l) bb Backgrounds: top, Wbb, Zbb… M H >130 GeV gg  H production with decay to WW Backgrounds: electroweak WW production…

Dmitri Denisov, ICHEP04, August SM Higgs Search: WH  l bb (M H <130 GeV) Ø DØ uses sample of W(e )+2 b tagged jets  Require exactly 2 jets to suppress top background 2.5 events expected and 2 events observed  (WH)xBR(H  bb) < 12.4 pb at 95% C.L. For M H =115 GeV Future improvements Extend b-tagging acceptance, efficiency Additional kinematic variables Better M bb resolution Add bb channel CDF uses e and  channels Requires at least 1 jet b tagged

Dmitri Denisov, ICHEP04, August SM Higgs Search: H  WW  l l  (M H >130 GeV) Search strategy:  2 high P t leptons and missing E t  WW comes from spin 0 Higgs: leptons prefer to point in the same direction DØ Run II Preliminary Higgs of 160 GeV W+W+ e+e+ W-W- e-e- n H

Dmitri Denisov, ICHEP04, August Current Limits on SM Higgs Search Ø DØ light (115 GeV) Higgs search limit  (WH)xBR(H  bb) < 12.4 pb -1 at 95% C.L. Both experiments set 95% C.L. on SM Higgs cross section x Br Limits already exceeding Run I results

Dmitri Denisov, ICHEP04, August Tevatron SM Higgs Search: Outlook Updated in 2003 in the low Higgs mass region W(Z)H  l (,ll)bb to include  better detector understanding  optimization of analysis Sensitivity in the mass region above LEP limit starts at ~2 fb -1 Meanwhile  optimizing analysis techniques  understanding detectors better  searching for non-SM Higgs with higher production cross sections or enhanced branching into modes with lower backgrounds LEP Tevatron Ldt, fb -1

Dmitri Denisov, ICHEP04, August Search for MSSM Higgs MSSM predicts larger Higgs cross sections for some values of parameter space then SM Ø Using NLO cross section calculations and assuming no difference between A and h/H DØ performs search for MSSM Higgs  multi-jet high E t sample  3 or more jets b tagged

Dmitri Denisov, ICHEP04, August Search for MSSM Higgs CDF searches for With A decaying into  pair  ~8% branching at high tan   lower backgrounds then bb pairs No excess seen over backgrounds

Dmitri Denisov, ICHEP04, August Search for H ++ /H -- Predicted by some beyond SM models like Left-Right Symmetric Models If short lived:  prominent signature – multiple high P t leptons, like sign di-lepton mass peak  backgrounds: WZ, W+jets, conversions (e) If long lived (c  > 3 m):  two high ionization tracks q q l + l - */Z*/Z H -- H ++ M H >134GeV D0 (113 pb -1 ) M(H L ) > 118 GeV (  ) at 95% C.L. CDF (240 pb -1 ) M(H L ) > 136 GeV (  ) at 95% C.L. Background < 10 -5

Dmitri Denisov, ICHEP04, August Tevatron Top and Higgs: Summary Top studies are actively progressing:  updated  tt, m t, limits on single top production  studies of SM predictions and beyond SM models  W helicity studies  decay modes: Wq, WX, Xq...  tt resonances,… Many excellent talks about top and Higgs studies at Tevatron are presented at ICHEP04 EW, Beyond SM, Heavy Quarks sessions Higgs search is in progress:  SM Higgs  sensitivity (m H >114 GeV) starts at ~2 fb -1  non-SM Higgs  many different models tested  already see reduction in allowed phase space (Run I, LEP) Expect substantial improvements in top studies, Higgs hunting with ~0.5 fb -1 already on tapes ~8 fb -1 expected in Run II No deviations from SM observed (yet)

Dmitri Denisov, ICHEP04, August Expected Run II Top Quark Studies Accuracy

Dmitri Denisov, ICHEP04, August Search for H   In the SM Higgs   has Br~10 -3  search for SM Higgs decaying to gamma pair is not practical at Tevatron Many SM extensions allow enhanced gamma pair decay rate largely due to suppressed coupling to fermions  Fermiphobic Higgs  Topcolor Higgs Search strategy: Look for peaks in  mass spectrum for high P t isolated  ’s

Dmitri Denisov, ICHEP04, August Experimental Challenges Collecting data at energy frontier is non- trivial Large particle fluxes  irradiation issues Small bunch spacing and large number of interactions per crossing  event synhronization  complex event topology Unexpected… CDF central tracking chamber  aging resolved Not new physics, just welding induced noise  resolved

Dmitri Denisov, ICHEP04, August Resonances in tt system? M X > 560 GeV No resonance production in tt system is expected in SM Some models predict tt bound states, example: topcolor-assisted technicolor  predicts leptophobic Z’ with strong 3 rd generation coupling Experimental check: search for bumps in tt effective mass spectrum Ø, 125 pb -1 DØ, 125 pb -1 Background Top Total