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Recent Results from the Tevatron

Recent Results from the Tevatron. Alison Lister UC Davis. Outline. The Tevatron and Experiments CDF XFT trigger Upgrade ‘Bread and Butter’ Physics Precision measurements of SM processes The ‘Known Knowns’ Recent observations The ‘Unknown Knowns’ SM Higgs Searches The ‘Unknown Unknowns’

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Recent Results from the Tevatron

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  1. Recent Results from the Tevatron Alison Lister UC Davis Alison Lister, UC Davis

  2. Outline • The Tevatron and Experiments • CDF XFT trigger Upgrade • ‘Bread and Butter’ Physics • Precision measurements of SM processes • The ‘Known Knowns’ • Recent observations • The ‘Unknown Knowns’ • SM Higgs Searches • The ‘Unknown Unknowns’ • Beyond SM Searches Alison Lister, UC Davis

  3. Design 1500 pb-1 2007 750 pb-1 Base 2005 2004 2006 2003 Fiscal Years Tevatron Performance • Many improvements over last year • More pbars, more reliably • Monthly integrated luminosity increased 25  45 pb-1 • Peak luminosity increased 180e30  292e30 cm-2 s-1 • Expect ~6-7 fb-1 by Oct. ‘09 Thanks to the Accelerator Division! Alison Lister, UC Davis

  4. CDF II Symmetric around beam axis Front-back symmetric 1.4 Tesla solenoid ~100 tons Dedicated silicon detector for secondary vertex tagging Muon coverage up to || ~ 1.1 Electron reconstruction up to || ~ 2.8 Alison Lister, UC Davis

  5. DØ II Symmetric around beam axis Front-back symmetric Solenoid + Toroid magnets Liquid argon compensating calorimeter June 2006: Start of Run IIb First data with L0 silicon detector Alison Lister, UC Davis

  6. 3.3 fb-1 2.7 fb-1 CDF + DØ • Integrated luminosity • ~3.3 fb-1 by July 2007 • About half-way to expected data size • Data taking efficiency • CDF + DØ ~87% • Starting/stopping runs • DAQ/hardware problems • Trigger dead-time • ~80% of delivered luminosity is used in analyses Took >2 years of collisions to get to stable high efficiency Alison Lister, UC Davis

  7. CDF Trigger Upgrades • Peak luminosity increasing • Close to design luminosity • Record is 282e30 • Trigger rates grow rapidly with instantaneous luminosity • Mostly due to ‘fakes’ and not real physics 300e30 CMX inclusive high pT muons default • CDF 3-tier trigger system limited by bandwidth at L2 • Adding pre-scales to triggers to keep rates down compromises physics goals • Series of trigger upgrades to keep high efficiency while reducing rates Alison Lister, UC Davis

  8. SL7 SL6 + SL5 SL4 SL3 (stereo) Z in SL7 pixel(SL7) (axial) pixel(SL5) - SL5 has opposite stereo angle (stereo) (axial) (stereo) + - Z in SL5 pixel(SL3) XFT Trigger Upgrade • COT (Central Outer Tracker) • 4 axial superlayers • 4 stereo superlayers • eXtremely Fast Tracker (XFT) • Track triggering system • Affects ~80% of all CDF physics • Before upgrades • Only using axial superlayers • XFT L1 upgrade • Confirm axial track passes through stereo layers and rough alignment of track in 3D • Gain factor 3-4 in rate Real tracks Reject Fakes ! Commissioned Oct 2006 Alison Lister, UC Davis

  9. L1 confirmed default L2 pointing XFT L2 Upgrade • Use full stereo information to reconstruct tracks in 3D and combine with information from outer detector components • Rate reduction factor 4 - 3.4 • Efficiency for well reconstructed muons ~99% • Combination of L1 and L2 XFT upgrades should take us safely beyond the Tevatron design luminosity Fermilab Engineer S.Holm about the system: “The most difficult firmware in my 25-year experience” Commissioning this autumn Alison Lister, UC Davis

  10. Latest Results for LP07 • 51 (42) new results from CDF (DØ) shown at LP07 conference • 31 from CDF using full data up to April 2007 (2.2 fb-1) • All areas covered from precision measurements of the W mass to MSSM Higgs searches • Many searches using “state of the art” techniques • Neural Networks • Matrix Element • Decision Trees • … Alison Lister, UC Davis

  11. More data Better understanding of ‘backgrounds’ ~9 orders of magnitude Tevatron Sensitivities • 1st Physics [few 100 pb-1] • Heavy flavor physics, inclusive W/Z, re-establish top • Now [1-2 fb-1] • Precision Mt, Bs-Mixing,Top properties, Observation of rare processes • Looking Ahead [? fb-1] • Even rarer processes, New Physics searches, Higgs • ‘The’ unexpected The focus is now to uncover the unknown Alison Lister, UC Davis

  12. ‘Bread and Butter’ Physics Alison Lister, UC Davis

  13. 1.0 fb-1 W+ c-jet Cross-Section • Select W + jets sample from lepton + jets final state • W + c-jet sample • Jet tagged with muon • pT>20 GeV/c and ||<2.5 • W→l (l=e, μ, where  decays leptonically) • Lepton pT>20 GeV/c and Missing transverse energy > 20 GeV • Exploit correlation between charges of leptons • Background: same sign • Signal: opposite sign Important background for ttbar and Higgs Can constrain s-quark PDF W+c-jet fraction = 0.071 ± 0.017 In agreement with LO theoretical predictions Alison Lister, UC Davis

  14. 1.6 fb-1 CP Violation in B±→J/ K± • Looking for charge asymmetry in b→c cbar bbar and conjugate • Asymmetry sensitive to new physics • Use kaon charge tag • Exploit polarity reversal of magnets to remove detector bias • Need careful modeling of kaon asymmetry due to different inelastic cross-sections in detector • K+N→ has no K-N counterpart • Unbinned fit to signal • Likelihood fit parametrisastion of backgrounds ACP(B+→J/ K+)= 0.0067± 0.0074 (stat.) ± 0.0026 (syst) Factor 2 better precision than world average Consistent with SM predictions of ~1% Alison Lister, UC Davis

  15. 0.2 fb-1 W Mass • Template fit to • Transverse Mass • Transverse Momentum • Transverse Missing Energy • Using their own fast MC simulation • Data driven shape constraints • 63 964 W→e events • 51 128 W→μ events Momentum scale calibration MW = 80413 ± 34 (stat) ± 34 (syst) MeV/c2 Alison Lister, UC Davis

  16. 1.2 fb-1 Top Mass • Many methods with improvements and more data • Some new ideas • e.g measuring the mass using cross-section constraint • In dilepton channel (l=e, μ) • Under-constrained system solved using ttbar longitudinal momentum • Replacing statistical with theoretical uncertainties • Sensitive to kinematics of events as well as number of events • 70 events pass all selection criteria Mt =170.7 +4.2-3.9 (stat.) ± 2.6 (syst.) ± 2.4 (theory) GeV/c2 Alison Lister, UC Davis

  17. 1.1-1.8 fb-1 Top Mass March 2007 • This autumn big CDF publication push for all analyses with 2.2 fb-1 • Expect ~10 new measurements since latest combination Is it looking less and less SM-like or is that just me? DØ-CDF Joint Systematics Effort Underway! New combinations will follow… Alison Lister, UC Davis

  18. Finding the ‘Known Knowns’ Alison Lister, UC Davis

  19. Diboson Results SM t-channel Triple Gauge Couplings? s-channel Alison Lister, UC Davis

  20. 1.9 fb-1 WZ Production • WZ→l’ll • 3 isolated lepton • e,μ,→e,μ • One > 25 Gev, other 2 > 10 GeV • Missing ET (for the ) > 25 GeV • Clean signal but BR only 1.8% • 2 leptons • opposite sign, same flavour, Z mass window • Fit using log likelihood ratio (WZ) = 4.1 +1.3-1.0(stat) ± 0.2(syst) ± 0.3(lumi) Lepton composition (t=track) In agreement with NLO prediction Alison Lister, UC Davis

  21. 1.9 fb-1 WWZ Couplings • Anomalous coupling limits set using pT distribution of Z-boson • Fit data using binned log likelihood to 3 parameters , g and  for 2 different values of  (1.5 and 2.0 TeV) NLO MCFM Consistent with SM NLO without triple gauge coupling Alison Lister, UC Davis

  22. 1.3 fb-1 b-Direct Observation • Many new baryon discoveries this past year • b-(dsb) one quark from each generation • Fully reconstruct exclusive decay • Sign of charge of tracks • Reconstructed displaced vertices • Masses and impact parameter resolution of reconstructed vertices • Angular separation between tracks • Minimum pT requirements • Use + for background studies • wrong-sign • Interpretation of peak as b- using unbinned likelihood Peak: 5.5 significance M(b-) =5.774 ± 0.011(stat) ± 0.015(syst) Alison Lister, UC Davis

  23. 0.9 fb-1 Evidence for Single Top • SM:  ~ 3 pb and rate |Vtb|2 • Combine 3 analyses • Decision Tree • Matrix Element Method • Bayesian Neural Network • Best Linear Unbiased Estimate • Assume SM ratio between s- and t-channel cross-sections Boosted Decision Trees Combined: 3.6 significance Multivariate techniques can coax signal out from large backgrounds Alison Lister, UC Davis

  24. Trying to find the ‘Unknown Knowns’ Alison Lister, UC Davis

  25. SM Higgs Production + Decay • Direct production gg→H • Highest Production rate • Largest background • Associated production ZH/WH • Leptonic vector boson decay helps for triggering and signal extraction Decay modes • Low Mass (MH<135 GeV/c2) • H→bb mode dominates • High Mass (135<MH<200 GeV/c2) • H→WW mode dominates • Intermediate Mass (MH ~135 GeV/c2) • Particularly difficult Alison Lister, UC Davis

  26. 1.9 fb-1 SM H→WW*→ll • Most sensitive channel for high mass Higgs • 2 leptons: e,,→e, • Must have opposite signs • Using Matrix Element Method • Event probability density from LO matrix elements from MCFM • Data compared to NNLL calculation for different mass hypotheses Limit at 2.0*SM for MH=160 GeV/c2 Looks like CDF was lucky this time… Alison Lister, UC Davis

  27. Run 1 0.1 fb-1 0.3-1.0 fb-1 1-2 fb-1 SM Higgs Limits 0.9-1.9 fb-1 The Tevatron experiments are doing much better than √(∫ lumi) Alison Lister, UC Davis

  28. SM Higgs Limits 0.9-1.9 fb-1 • Combining all limits from all channels as well as between CDF and D0 Alison Lister, UC Davis

  29. SM Higgs Limits 0.9-1.9 fb-1 • Projections based on 2 x D0 results (for CDF + D0) • Assuming better than √(∫ lumi) • Reducing systematics, increasing acceptance, including more channels () Alison Lister, UC Davis

  30. Looking for the ‘Unknown Unknowns’ Alison Lister, UC Davis

  31. Deviations from SM • New CDF web-page “Discovery Watch” (soon to be made public) Alison Lister, UC Davis

  32. SUSY + mSUGRA • SUSY is one of the more popular extensions to the SM • mSUGRA • SUSY symmetry broken by gravity at GUT scale • 5 parameters: m0, m1/2, tan , A0, sign(µ) • Previous Tevatron squark/gluino searches using Jet and large MET • Mainly arising from decay of LSP • High tan  • Squarks decay to charginos and neutralinos • Final states with leptons • Some models stau might be lightest lepton • Enhanced cross-section to taus • Squarks lighter than gluinos Alison Lister, UC Davis

  33. 0.96 fb-1 tan = 15 A = -2m0 µ<0 LEP slepton searches LEP chargino searches SUSY: Squarks with Jet, h, MET • ≥2 jets (∆12>165˚,ET>35 GeV, ||<0.8) • MET ≥ 175 GeV • At least one isolated hadronically decaying  (ET>15 GeV, ||< 2.5) • Separate hfrom jets and electrons using loose cuts to NN outputs • HT = ET + ETjet1+ ETjet2 ≥ 325 GeV • Main backgrounds: Z(→)+jets, ttbar,W+jets • Modeled by ALPGEN+PYTHIA • QCD negligible after selection • -decays simulated by TAUOLA • Dominant systematic Jet Energy Scale • 2 observed events Alison Lister, UC Davis

  34. t’ Search 0.76 fb-1 • Massive 4th generation top-like quark • Predicted by some SUSY models (beautiful mirrors), Little Higgs • Generic 4th chiral generation allowed by EWK data; can accommodate a heavy Higgs (~500 GeV) without any other new particles • Looking for interesting events on the tails of distributions • Analysis will be re-done with ~2.2 fb-1 making use of heavy-flavour tagging to hopefully increase sensitivity Exclude with 95% CL t´ mass below 256 GeV/c2 Alison Lister, UC Davis

  35. Couple of Strange Events… Alison Lister, UC Davis

  36. High Mass Resonances in ee 0.9 fb-1 • Model independent search for high mass narrow resonances • Scan Mass region 150-500 GeV/c2 in 5 GeV/c2 steps • Assume narrow resonance • Model with Gaussian of width equal to detector resolution • Fit distribution to background only and background + narrow resonance • Estimate probability of background giving 2 as large as largest deviation: 1.7% ? Excess around 240 GeV/c2 Alison Lister, UC Davis

  37. Model Independent Searches 0.9 fb-1 • VISTA • Model independent approach that looks at gross features of the data • Sensitive to new large cross-section physics • Partitioning of events into exclusive final states • e,µ,,,jet,missing pT, … • Global comparison to SM predictions from PYTHIA, MADEVENT and/or HERWIG • 16’486 kinematic distributions from 344 exclusive final states • 409 distributions with deviation > 5 • None believed to have new physics interpretation Alison Lister, UC Davis

  38. 0.9 fb-1 SLEUTH • Quasi-model independent approach emphasizes the high-ΣpT tails • Particularly sensitive to new electroweak scale physics • Looks at one variable: ΣpTfor all final states • Uses correction factors to SM predictions found by VISTA • SLEUTH determines most interesting region of tail • Same-sign e mu + 2 jets + MET final state • 4 data events observed • 0.71 SM events predicted • 2.5 sigma effect (stat only) Alison Lister, UC Davis

  39. Status of the SM • Very rich and diverse physics program • “Looking in most nooks and crannies” • Background understanding improving • Small systematic uncertainties in searches • Experiments found many new processes expected by SM • Sensitive to beyond SM • Higgs discovery at Tevatron looks much exciting than it did a year ago • New results expected in next year • Model dependent and model independent searches showing “noise” above SM predictions but nothing concrete EWK fit: MH<182 GeV/c2 (incl. LEP direct exclusion) We know something is out there but what and where? Alison Lister, UC Davis

  40. Backup Slides Alison Lister, UC Davis

  41. 1.1-1.5 fb-1 Evidence for ZZ • ZZ→llll and ZZ→ll (l = e or ) • Systematics • Mostly dominated by cross-section uncertainty of back-ground processes • Drell-Yan the missing ET is dominant • W+jets dominated by lepton fake rate Likelihood ratio plot for ll Measured: (ZZ) = 0.75 + 0.71- 0.54 pb SM NLO: (ZZ) = 1.4 ± 0.1 pb Consistent with SM without triple gauge coupling Alison Lister, UC Davis

  42. 1.1-2.2 fb-1 B Baryon Discoveries b b b Alison Lister, UC Davis

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