1 / 39

Recent Results from D Ø

Recent Results from D Ø. Barbro Åsman Stockholm University For the DØ Collaborations. CDF. 6 km circumference. D Ø. 3RD INTERNATIONAL WORKSHOP ON HE INTERCONNECTION BETWEEN PARTICLE PHYSICS AND COSMOLOGY University of Oklahoma, Norman , OK, US May 18-22 2009. Tevatron Accelerator.

nayef
Download Presentation

Recent Results from D Ø

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent Results from DØ BarbroÅsman Stockholm University For the DØ Collaborations CDF 6 km circumference DØ 3RD INTERNATIONAL WORKSHOP ON HE INTERCONNECTION BETWEEN PARTICLE PHYSICS AND COSMOLOGY University of Oklahoma, Norman , OK, US May 18-22 2009

  2. Tevatron Accelerator • Excellent performance: • Instantaneous luminosity: • Typical : ~2.8x1032 cm-2s-1 • Record : 3.3x1032 cm-2s-1 • Delivered ~6.5 fb-1 • Recorded ~5.7 fb-1

  3. The DØ Detector • Multipurpose detector • Central tracking system: • Silicon vertex detector Fiber tracker • Preshowers • Calorimeters • Muon system

  4. Outline • Introduction • Bs-Physics • CP Violation • Rare Decay • W mass and Top mass • Single Top • Higgs • New Phenomena • Conclusion

  5. CP Violation in Bs Decays Mass eigenstates: assl=Γs/ΔMs tan(φs) -(8.4+5.2-6.7)·10-3 0.002 ± 0.009·10-3 assl = assl = World Average assl = +0.02·10-3 in SM

  6. CP Violation in B0s Decay Opposite Side Reconstructed Side X μ+ B μ(e) LT π- D-S φ ν K- K+ -(8.4+5.2-6.7)·10-3 0.002 ± 0.009·10-3 assl = assl =

  7. Rare Decays: B0s→μ+μ‐ -> Expect 0 Events at Tevatron Can be enhanced by New Physics Contributions B(Bs-> μμ) =(3.37±0.31)×10-9

  8. B0s→μ+μ‐: Significance & Outlook RESULT: B(B0s -> m+m-) < 4.3(5.3 ) x 10-8 Expect sensitivity to get Better. Detector and analysis improvements Expect combined limit O(10-8) by end of Run II Significant constraints on New Physics

  9. Masses for W -Top - Higgs t W b H • Constraint on SM Higgs mass dominated • by the W mass uncertainty: • Dmt = ±1.2 GeV  DMH = +9/-8 GeV • DMW = ±25 MeV  DMH = +17/-13 GeV • Measured from template fits to • W transverse mass, lepton pT and MET distribution • Exquisite understanding of the detector response, noise and pileup required: • ~ few MeV for quantities ~40 GeV! • Uncertainty currently dominated • by statistics of Z sample used for calibration. • Theoretical uncertainties ~10-15 MeV. W W W

  10. W Mass –W -> eν mode – Cannot measure ν or W momentum along beam Use variables defined in transverse plane - Cannot predict analytically Distributions from parametric simulation the work goes here! e+ PTe, MET, mT mT = √ 2 PTe, MET (1-cos Df)

  11. Mass Fits mZ = 91.185 ± 0.033 GeV (stat) Z mass value from LEP was an input to electron energy scale calibration, PDG: mZ = 91.1876 ± 0.0021 GeV mW= 80.401 ± 0.023 GeV (stat)

  12. Summary of Uncertainties

  13. W Mass Results • Single most precise • measurement • Good agreement with • previous measurements • Based on 1/6 of the data

  14. Top Quark Mass • Dileptons: • e, m, t -> e or m 6,5 % low background • e or m + t -> had 3.6 % resonable background • Leptons plus jets: • e, m, t -> e or m + jets 35 % resonable background • t -> had + jets 9.5% high background All jets: 46 % high background

  15. Top Mass Measurement • Sophisticated techniques to minimize statistical and systematic uncertainties. Leptons + jets RunIIa : 171.5 ± 1.4 (stat) ± 1.8 (syst) with 1.0 fb-1 Lepton + jets RunIIb: 174.8 ± 1.0 (stat) ± 1.6 (syst) with 2.6 fb-1 Electron + muon RunIIa: 171.7 ± 6.4 (stat) ± 2.5 (syst) with 1.0 fb-1 Electron + muon RunIIb: 176.1 ± 3.9 (stat) ± 2.7 (syst) with 2.6 fb-1 ee, mm, l + track RunIIa: 174.2 ± 6.0 (stat) ± 2.3 (syst) with 1.0 fb-1

  16. Top Mass Combined Measurement Goal to reach an error below 1 GeV

  17. Observation of Single Top Direct access to the Wtb coupling Overall rate and ratio between s -and t-channels are sensitive to NP• Experimental challenge: -cross section ~x2 lower than ttbar -large backgrounds from W+2 jets -S/B ~1/200 before b-tagging -Need multivariate techniques to extract signal.

  18. Observation of Single Top s (pp -> tb + X, tbq + X) = 3.94 ± 0.88 pb | Vtb | > 0.78 at 95 % C.L. | f1L Vtb | = 1.07 ± 0.12 where is f1L the strength of the left-handed Wtb coupling Submitted to PRL (2009), hep-ex/0903.0850

  19. Top Resonances? Seach for X -> tt 0.35 TeV < MX< 1.2 TeV Width RX = 0.012 MX Signal: Lepton, MET, ≥3 jets, ≥1b-tag

  20. Higgs Search …and more! • Current experimental information : • SM LEP direct search: mH>114 GeV • SM indirect constraint: mH<168 GeV • Tevatron is sensitive over whole “interesting” mass range. • Main production mechanisms: • Gluon fusion ggH • Associated production , WH and ZH: • Dominant decay channels: • mH<135 GeV: Hbb • mH>135 GeV: HWW(*) • Search strategy: • Low mass region: • WHlnbb, ZH l+l-bb, ZHnnbb • High mass region: • ggHWW(*) l+nl’-n

  21. Higgs Channels

  22. Higgs Limits

  23. Higgs Limits

  24. SUSY Higgs Minimal Supersymmetric Standard Model (MSSM): 5 Physical Higgs bosons : 3 Neutral: (A0, h0 and H0) → 0 2 Charged: H Two parameters to calculate Higgs masses and couplings at tree level mA tan(b) = ratio of vacuum expectation values of two Higgs fields b, t+ b, t- • DØ search: • MSSM at largetan: • 0={h0/H0,A0} nearly degenerated in mass • Coupling to b, t enhanced (tan)  +X  2 x tan2 • BR(0bb)~90%, BR(0t+t-)~10% t+ t-

  25. F0 -> bb /F0 -> tt Φ0->bb too hard due to QCD processes: •Look for Φ0b->bbb in triple‐tagged events to reduce background Combination with analysis on earlier data: Exclusion region in the tanβ‐mA plane • F0 -> tt has lower BR, • but higher cross section • •Inclusive decays: F -> τeτμ, τhτμ, τhτe • •Challenge: hadronic τ -decay ID

  26. NMSSM h -> aa Search • h -> bb branching ratio reduced • h decays mainly to pair of pseudo-scalor Higgs a : h ->aa • LEP search sets limit: Mh > 82 Gev • For Masses 2Mm < Ma < 2Mt • - BR(a->m+m-) ~ 100%: 4 m final state • - signature: two pair of extremely • collinear m due to low Ma • Require “companion-track” for each of • two muon → m isolation for pair. IF: Cross section of ~ 1000 fb Mh =120 GeV BR(aa -> mm) > 10% exluded 95% CL BR(h-> aa) ~ 1

  27. NMSSM h -> aa Search For Masses 2Mt < Ma < 2Mb Decays mainly to t pairs - 2m2t final state : one pair of collinear m large MET from a → t+t-decay Select back-to-back mm- and tt-paired topologies

  28. SUSY Searches Chargino/Neutralino • Clean multi-lepton+MET signature, but: • low sxBR (<0.1 pb) • low pT leptons (<8 GeV) • Challenges: lepton ID at low pT

  29. SUSY Searches • Pair production of q,g with decays involving multi-jets + MET. • Critical to understand tail of MET distribution.

  30. Model Independent Search Look for discrepancies between data and expactions High PT isolated lepton 4/180 channels with disagreement m±MET + 2 jets 9.3 s m±gMET + 1 jet 6.6 s m+m-MET (OS) 4.4s m+m-g (OS) 4.4 s • VISTA • Event counts in many final states • Shapes of many kinematic • variables

  31. Model Independent Search • Sleuth • Focus on tail of SPT for each final • state • Search for excesses 5/44 distributions with some discrepancy 1/ 44 with significant discrepancy probably bad m resolution

  32. Tau Sneutrinos (RPV) q Look for high PT isolated lepton pair Assume that nt is the LSP Assume that all RPV couplings are zero except l’311, l321=l312 Limits on s*BR give nt mass limits for different values of l e- ~ n q ¯ m+

  33. Conclusions • Run II physics program in full swing. • Excellent performance of the accelerator and CDF and DØ detectors. • Expect more than 8 fb-1 by the end of the run. • Analyzed luminosity will increase by a factor of ~2.5-7. • Physics reach further expanded by analysis improvements. • Establish benchmarks in analysis techniques for the LHC era. • Prospects for discoveries remain open.

  34. Charge Massive Stable Particles • Charge Massive Stable Particles CMSPs or Champs • -”stable” -> lifetimes > ~10-8 sec • Extension of the SM • -> stop, stau or chargino in some SUSY models • -> possibly long-lived if mass difference to decay product • e.g. chargino neutralino + X and neutralino is LSP CMSPs may appear as "slow" moving muons. Striking signature: - isolated high pTmuons - use timing in muon system (D0) or central track TOF - the di-muon mass can also provide discrimination

  35. CMSP - pair-production limits: σ∼ 40 fb for M~ 200 GeV - SUSY limits model dependent no stau limit ~ ~ c1+ c1+ m > 171 higgsino-like m > 206 guagino-like

  36. D0: 2 isolated μ pT>20 GeV - |φμμ+θμμ−2π| > 0.05 plus timing cuts to reject cosmic ray muons - backgrounds determined from

  37. Fermiophobic Higgs Search • Higgs mainly couples to bosons -> • branching ratio to fermion supressed • - Decays to g or W

  38. WH-> WWW*-> l±nl±n+X Likelihood discriminant used to separate signal from backgrounds: - physics: WZ -> lnll with lost lepton from Z - QCD b-jets, punch-throughs, g -> e - Charge flips: maily from Z/g* -> ll ee Data: 19 events Bckg: 20.4 ± 4.0 mm Data: 5 events Bckg: 5.0 ± 2.5 em Data: 15 events Bckg: 18.0 ± 2.8

  39. H-> gg Search for di-photon mass peak Mass resolution ~ 3 GeV / c2 Looser selection PTgg > 35 GeV/c Backgrounds from MC and Data No excess observed: Excluded MH<102.5 GeV /C2 @ 95 CL

More Related