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This lecture discusses the latest physics results from the Tevatron accelerator, including the observation of Bs-mixing, new baryon states, charmless B decays, and evidence for Do-Dobar mixing. Precision measurements of the W and top masses, as well as the discovery of the WZ and ZZ bosons, are also highlighted. The lecture concludes with the search for Higgs boson decays to top quarks and measurements of the Z and W boson cross sections.
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Physics at the Tevatron XXXVI International Meeting on Fundamental Physics From IMFP2006 → IMFP2008 Rick Field University of Florida (for the CDF & D0 Collaborations) 2nd Lecture Bosons, Top, and Higgs Palacio de Jabalquinto, Baeza, Spain CDF Run 2 Rick Field – Florida/CDF/CMS
23 tt-pairs/month! Tevatron Performance The data collected since IMFP 2006 more than doubled the total data collected in Run 2! IMFP 2008 ~3.3 fb-1 delivered ~2.8 fb-1 recorded ~1.6 fb-1 IMFP 2006 ~1.5 fb-1 delivered ~1.2 fb-1 recorded Integrated Luminosity per Year • Luminosity records (IMFP 2008): • Highest Initial Inst. Lum: ~2.92×1032 cm-2s-1 • Integrated luminosity/week: 45 pb-1 • Integrated luminosity/month: 165 pb-1 • Luminosity Records (IMFP 2006): • Highest Initial Inst. Lum: ~1.8×1032 cm-2s-1 • Integrated luminosity/week: 25 pb-1 • Integrated luminosity/month: 92 pb-1 Rick Field – Florida/CDF/CMS
Many New Tevatron Results! Some of the CDF Results since IMFP2006 • Observation of Bs-mixing: Δms = 17.77 ± 0.10 (stat) ± 0.07(sys). • Observation of new baryon states: Sb and Xb. • Observation of new charmless: B→hh states. • Evidence for Do-Dobar mixing . • Precision W mass measurement: Mw = 80.413 GeV (±48 MeV). • Precision Top mass measurement: Mtop = 170.5 (±2.2) GeV. • W-width measurement: 2.032 (±0.071) GeV. • WZ discovery (6-sigma): s = 5.0 (±1.7) pb. • ZZ evidence (3-sigma). • Single Top evidence (3-sigma) with 1.5 fb-1: s = 3.0 (±1.2) pb. • |Vtb|= 1.02 ± 0.18 (exp) ± 0.07 (th). • Significant exclusions/reach on many BSM models. • Constant improvement in Higgs Sensitivity. I cannot possibility cover all the great physics results from the Tevatron since IMFP 2006! I will show a few of the results! Rick Field – Florida/CDF/CMS
Z-boson Cross Section (CDF) L = 72 pb-1 IMFP2006 QCDDrell-Yan • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)! Rick Field – Florida/CDF/CMS
Z-boson Cross Section (CDF) IMFP2006 L = 337 pb-1 • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)! Rick Field – Florida/CDF/CMS
New since IMFP2006 Zcc Zcp Zpp Z-Boson Rapidity Distribution • Measure ds/dy for Z→e+e-. Use electrons in the central (C) and plug (P) calorimeter. • Parton momentum fractions x1 and x2 determine the Z boson rapidity, yZ. • Production measurement in high yZ region probes high x region of PDF’s. • Plug-plug electrons, ZPP, are used to probe the high x region! Plug-Plug electrons! 1.1fb-1 91,362 events 66 < MZ < 116 GeV Rick Field – Florida/CDF/CMS
New since IMFP2006 Z-Boson Rapidity Distribution • CDF measured ds/dy for Z/g* compared with an NL0 calculation using CTEQ6.1M PDF. • The NLO theory is scaled to the measured s(Z)! • No PDF or luminosity uncertainties included. NLO + CTEQ6.1 PDF NLO + MRST PDF NLL0 + NNL0 MRST PDF Rick Field – Florida/CDF/CMS
Channel for Z→ττ: electron + isolated track One t decays to an electron: τ→e+X (ET(e)> 10 GeV) . One t decays to hadrons: τ → h+X (pT > 15GeV/c). Remove Drell-Yan e+e- and apply event topology cuts for non-Z background. Signal cone Isolation cone The Z→tt Cross Section (CDF) • Taus are difficult to reconstruct at hadron colliders • Exploit event topology to suppress backgrounds (QCD & W+jet). • Measurement of cross section important for Higgs and SUSY analyses. • CDF strategy of hadronic τ reconstruction: • Study charged tracks define signal and isolation cone (isolation = require no tracks in isolation cone). • Use hadronic calorimeter clusters (to suppress electron background). • π0 detected by the CES detector and required to be in the signal cone. • CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of EM calorimeter. Rick Field – Florida/CDF/CMS
1 and 3 tracks, opposite sign same sign, opposite sign The Z→tt Cross Section (CDF) • CDF Z→ττ (350 pb-1): 316 Z→ττ candidates. • Novel method for background estimation: main contribution QCD. • τ identification efficiency ~60% with uncertainty about 3%! IMFP2006 264 ± 23 (stat) ± 14 (sys) ± 15 (lum) Rick Field – Florida/CDF/CMS
Higgs → tt Search (CDF) events IMFP2006 140 GeV Higgs Signal! 1 event • Data mass distribution agrees with SM expectation: • MH > 120 GeV: 8.4±0.9 expected, 11 observed. • Fit mass distribution for Higgs Signal (MSSM scenario): • Exclude 140 GeV Higgs at 95% C.L. • Upper limit on cross section times branching ratio. Rick Field – Florida/CDF/CMS
New since IMFP2006 Higgs → tt Search (CDF) events events No Significant Excess of events above SM background is observed! Rick Field – Florida/CDF/CMS
W-boson Cross Section (CDF) W Acceptance • Extend electron coverage to the forward region (1.2 < |h| < 2.8)! IMFP2006 48,144 W candidates ~4.5% background overall efficiency of signal ~7% Rick Field – Florida/CDF/CMS
New since IMFP2006 W-Boson Mass Measurement • The Challenge: • Do not know neutrino pz. • No full mass reconstruction possible. • Extract from a template fit to PT, MT, and Missing ET. • Transverse mass: MW = 80413 ± 48 MeV/c2 Single most precise measurement to date! Rick Field – Florida/CDF/CMS
New since IMFP2006 W-Boson Width Measurement • Model transverse mass distribution over range 50-200 GeV. • Normalize 50-90 GeV and fit for the width in the high MT region 90-200 GeV. • The tail region is sensitive to the width of the Breit Wigner line-shape. Rick Field – Florida/CDF/CMS
W+ W- y antiproton proton e+ u W+ p p d u e W Production Charge Asymmetry • There are more u-quarks than d-quarks at high x in the proton and hence the W+ (W-) is boosted in the direction of the incoming proton (antiproton). • Measuring the W± asymmetry constrains the PDF’s! Q2 = 100 GeV2 MRST2004NLO xG(x,Q2) u d d u x u 10-3 10-2 10-1 1 Rick Field – Florida/CDF/CMS
New since IMFP2006 W Production Charge Asymmetry • Since the longitudinal momentum of the neutrino, pL(n), is not known the W rapidity cannot be reconstructed. • So previously one looked at the the electron charge asymmetry. • The V-A structure of the W+ (W-) decay favors a backward e+ (forward e-) which “dilutes” the W charge asymmetry! • New CDF measurement performed in W→en channel. • pL(n) is determined by constraining MW = 80.4 GeV leaving two possible yW solutions. Each solution receives a probability weight according to the V-A decay structure and the W cross-section, s(yW). • The process is iterated since s(yW) depends on the asymmetry. Rick Field – Florida/CDF/CMS
W + g Cross Sections (CDF) IMFP2006 ET(g) > 7 GeV R(lg) > 0.7 Rick Field – Florida/CDF/CMS
New since IMFP2006 W + g Cross Sections (CDF) ET(g) > 7 GeV R(lg) > 0.7 18.03±0.65(stat)±2.55(sys) ±1.05(lum) Rick Field – Florida/CDF/CMS
Z + g Cross Sections (CDF) IMFP2006 Note: (W)/(Z) ≈ 4 while (W)/(Z) ≈ 11 ET(g) > 7 GeV R(lg) > 0.7 Rick Field – Florida/CDF/CMS
New since IMFP2006 Z + g Cross Sections (CDF) 390 events ET(g) > 7 GeV R(lg) > 0.7 Meeg > 40 GeV/c2 Rick Field – Florida/CDF/CMS
The W+W Cross-Section IMFP2006 Campbell & Ellis 1999 Rick Field – Florida/CDF/CMS
The W+W Cross-Section (CDF) IMFP2006 L = 825 pb-1 We are beginning to study the details of Di-Boson production at the Tevatron! • WW→dileptons + MET • Two leptons pT > 20 GeV/c. • Z veto. • MET > 20 GeV. • Zero jets with ET>15 GeV and |h|<2.5. Observe 95 events with 37.2 background! Lepton-Pair Mass! Missing ET! ET Sum! Rick Field – Florida/CDF/CMS
New since IMFP2006 WW+WZ Cross-Section NLO Theory σWW × Br(W→ln, W→jj) = 12.4 pb × 0.146 = 1.81 pb σWZ × Br(W→ln, Z→jj) = 3.96 pb × 0.07 = 0.28 pb Rick Field – Florida/CDF/CMS
W+Z → trileptons + MET The Z+W, Z+Z Cross Sections IMFP2006 Observe 2 events with a background of 0.9±0.2! Upper Limits Rick Field – Florida/CDF/CMS
New since IMFP2006 The W+Z Cross Section Strategy • Search for events with 3 leptons and missing energy. • Small cross-section but very clean signal. • Anomalous cross-section sensitive to non SM contributions. 3.0 σ significance! Rick Field – Florida/CDF/CMS
New since IMFP2006 The Z+Z Cross Section Strategy: • Search for events with either 4 leptons or 2 leptons and significant missing ET. • Calculate a Prob(WW) or Prob(ZZ) based on event kinematics and LO cross section. • Construct a likelihood ratio. • Fit to extract the llnn signal. ZZ decaying into 2 leptons + MET ZZ decaying into 4 leptons 3.0 σ significance! Rick Field – Florida/CDF/CMS
New since IMFP2006 Higgs → W+W • We are within a factor of two of the standard model Higgs (160 GeV) → WW! Rick Field – Florida/CDF/CMS
Heavy Quark Production at the Tevatron • Total inelastic stot ~ 100 mb which is 103-104 larger than the cross section for D-meson or a B-meson. • However there are lots of heavy quark events in 1 fb-1! • Want to study the production of charmed mesons and baryons: D+, D0, Ds , lc , cc , Xc, etc. • Want to studey the production of B-mesons and baryons: Bu , Bd , Bs , Bc , lb , Xb, etc. with 1 fb-1 ~1.4 x 1014 ~1 x 1011 ~6 x 106 ~6 x 105 ~14,000 ~5,000 • Two Heavy Quark Triggers at CDF: • For semileptonic decays we trigger on m and e. • For hadronic decays we trigger on one or more displaced tracks (i.e. large impact parameter). CDF-SVT Rick Field – Florida/CDF/CMS
New since IMFP2006 B-Baryon Observations (CDF) The Tevatron is excellent at producing particles containing b and c quarks(Bu, Bd, Bs, Bc, b, b,b) b b bc Rick Field – Florida/CDF/CMS
Top Decay Channels • mt>mW+mb so dominant decay tWb. • The top decays before it hadronizes. • B(W qq) ~ 67%. • B(W ln) ~ 11% l = e, m, t. Rick Field – Florida/CDF/CMS
New since IMFP2006 s(tt) = 6.16 ± 1.05 (stat) ± 0.72 (syst) + 0.37 (lumi) pb s(tt) = 8.3 ± 1.5 (stat) ± 1.0 (syst) + 0.5 (lumi) pb Dilepton Channel (CDF) • Backgrounds: • Physics: Drell-Yan, WW/WZ/ZZ, Z tt • Instrumental: fake lepton • Selection: • 2 leptons ET > 20 GeV with opposite sign. • >=2 jets ET > 15 GeV. • Missing ET > 25 GeV (and away from any jet). • HT=pTlep+ETjet+MET > 200 GeV. • Z rejection. IMFP2006 84 events 65 events 20 events background Rick Field – Florida/CDF/CMS
s(tt) = 8.2 ± 0.5 (stat) ± 0.8 (sys) ± 0.5 (lum) pb s(tt) = 8.2 ± 0.6 (stat) ± 1.1 (syst) pb s(tt) = 8.8 ± 0.8 (stat) ± 1.2 (sys) ± 0.5 (lum) pb Lepton+Jets Channel (CDF) b-Tagging • Require b-jet to be tagged for discrimination. Tagging efficiency for b jets~50% for c jets~10% for light q jets < 0.1% 1 b tag IMFP2006 2 b tags ~70 events HT>200GeV ~180 events ~150 events ~45 events Small background! Rick Field – Florida/CDF/CMS
New since IMFP2006 Tevatron Top-Pair Cross Section CDF Run 2 Preliminary Theory Bonciani et al., Nucl. Phys. B529, 424 (1998) Kidonakis and Vogt, Phys. Rev. D68, 114014 (2003) Rick Field – Florida/CDF/CMS
New since IMFP2006 Top Quark Mass Leptons+Jets Channel Dilepton Channel Mt=170.4 ± 3.1(stat) ± 3.0(sys)GeV/c2 Rick Field – Florida/CDF/CMS
Top Cross-Section vs Mass Tevatron Summer 2005 CDF Winter 2006 CDF combined Cacciari, Mangano, et al., hep-ph/0303085 Rick Field – Florida/CDF/CMS
Tevatron Run I + LEP2 Constraining the Higgs Mass • Top quark mass is a fundamental parameter of SM. • Radiative corrections to SM predictions dominated by top mass. • Top mass together with W mass places a constraint on Higgs mass! Summer 05 114 GeV Higgs very interesting for the Tevatron! Rick Field – Florida/CDF/CMS
Strongly Produced tt Pairs g g Other Sources of Top Quarks • Dominant production mode NLO+NLL = 6.7 1.2 pb • Relatively clean signature • Discovery in 1995 ~85% ~15% ElectroWeak Production: Single Top • Larger background • Smaller cross section s≈ 2 pb • Not yet observed! Rick Field – Florida/CDF/CMS
Single Top Production tW associated production s-channel t-channel (mtop=175 GeV/c2) Run I 95% C.L. B.W. Harris et al.:Phys.Rev.D66,054024 T.Tait: hep-ph/9909352 Z.Sullivan Phys.Rev.D70:114012 Belyaev,Boos: hep-ph/0003260 Rick Field – Florida/CDF/CMS
Single Top at the Tevatron IMFP2006 95% C.L. limits on single top cross-section (2.9 pb) (0.9 pb) (2 pb) • The current CDF and DØ analyses not only provide drastically improved limits on the single top cross-section, but set all necessary tools and methods toward a possible discovery with a larger data sample! • Both collaborations are aggressively working on improving the results! Theory! Single Top Discovery is Possible in Run 2 !!!! - R. Field (IMFP2006) Rick Field – Florida/CDF/CMS
New since IMFP2006 Single Top Production DØ Combination 3.6s! Single Top Signal! 3.4s! Expected sensitivity: 2.1 s+t= 4.9 ±1.4 pb s= 1.0, t =4.0 pb First direct measurement of Vtb 0.68 <|Vtb|< 1 @ 95%CL or |Vtb| = 1.3± 0.2 PRL 98 18102 (2007) Rick Field – Florida/CDF/CMS
New since IMFP2006 Single Top Production 3.1s! s+t= 3.0 ± 1.2 pb s= 1.1, t =1.9 pb s+t= 2.7 ± 1.2 pb s= 1.1, t =1.3 pb Expected sensitivity: 3.0 Expected sensitivity: 2.9 Observed significance: 2.7 Rick Field – Florida/CDF/CMS
CDF Run II Preliminary L=1.5 fb-1 s-channel t-channel Z. Sullivan, Phys.Rev. D70 (2004) 114012 Measurement of |Vtb| (CDF) • Using the Matrix Element cross section measurement, CDF determines |Vtb| assuming |Vtb| >> |Vts|, |Vtd|! |Vtb|= 1.02 ± 0.18 (exp) ± 0.07(thy) DØ |Vtb|>0.68, |Vtb| = 1.3 ±0.2 Rick Field – Florida/CDF/CMS
Jet1 Lepton Jet2 Single Top Candidate Event • t-channel single top production has a kinematic peculiarity. • Distinct asymmetry in lepton charge Q times the pseudo-rapidity of the untagged jet! t-channel single top! EPD > 0.9 Central Electron Candidate Charge: -1, Eta=-0.72 MET=41.6 GeV Jet1: Et=46.7 GeV Eta=-0.6 b-tag=1 Jet2: Et=16.6 GeV Eta=-2.9 b-tag=0 Q×h = 2.9 (t-channel signature) EPD=0.95 CDF Run: 211883, Event: 1911511 Rick Field – Florida/CDF/CMS
New since IMFP2006 Single Top at the Tevatron Single top cross-section measurements! • Single top has (almost) been seen at the Tevatron at the expected rate! If you think 3.5s is enough to claim discovery? Rick Field – Florida/CDF/CMS
Top-AntiTop Resonances CDF Run 1 Excess is reduced! Phys.Rev.Lett. 85, 2062 (2000) • CDF observed an intriguing excess of events with top-antitop invariant mass around 500 GeV! Rick Field – Florida/CDF/CMS
New since IMFP2006 Top-AntiTop Resonances • The excess has disappeared! Excess is gone! Rick Field – Florida/CDF/CMS
Tevatron Measurements Jets b-quarks We are getting very close to the Higgs and/or new physics! W Z W+g Single top Z+g W+W tt W+Z Z+Z Rick Field – Florida/CDF/CMS