ＣＤＦ実験の最新結果

1. ＣＤＦ実験の最新結果 筑波大学数理物質研究科 佐藤構二 日本物理学会第61回年次大会 愛媛大学、2006年　3月27日

2. Tevatron Run II • p – p collisions at s = 1.96 TeV (1.8 TeV in Run I). • Run II started in Summer 2001. • Particle collider at the highest energy!

3. CDF Collaboration • ~600 people from 12 Countries.

4. Tevatron Run II — Luminosity Status • Peak Luminosity Record: 1.8  1032 cm2 s-1. • Weekly Record: 27 pb-1/week. • Integrated Luminosity • Delivered: 1.6 fb-1 ,Recorded: 1.3 fb-1. • Future: 4-8 fb-1 by 2009. • Recent analyses typically use 700-800 pb-1. Run II since Summer 2001

5. Collider Detector at Fermilab Multi-purpose detector • Tracking in magnetic field. • Coverage |h|<~1. • Precision tracking with silicon. • 7 layers of silicon detectors. • EM and Hadron Calorimeters. • sE/E ~ 14%/E (EM). • sE/E ~ 84%/E (HAD). • Muon chambers.

6. Contents • Top physics • Pair production cross section • Top mass • Search for ttbar resonance • Lifetime measurement • Search for single top • Direct search for Higgs Boson • Standard Model Higgs • B physics • Status of Bs oscillation • Bs rare decay • Bs and Bc properties

7. Top Physics

8. b q’ p Why is Top Physics Interesting? • Direct study on top is only possible at Tevatron. • Top is one of the least-well studied particles. • Does it couple to exotic particles? • Top mass is unexpectedly heavy ~35mb. • Special role in EWSB? • Top datasets at CDF-II (7xCDF-I) is finally enough to start detailed studies on top. W helicity Top Mass l+ Top Width Anomalous Couplings Top lifetime Production cross-section W+ CP violation Top Charge Resonance production p n t b Production kinematics _ X ttbar decay modes: _ ttbar Spin correlation _ t q Rare/non SM Decays W- _ Branching Ratios |Vtb|

9. Top Pair Cross Section • Cross section is sensitive to both production and decay anomaly. • The difference of the xs between different decay modes might indicate new physics. • CDF measures xs with various decay modes/methods, and the results are consistent with SM.

10. Top Mass Measurement  Motivation • Presise mass measurements of W and top can constrain the SM Higgs mass through radiative corrections. • From Tevatron Run I : • MW = 80454  59 MeV/c2 (World Average :80410  32 MeV/c2 ) • Mtop = 178.0  4.3 GeV/c2  Mhiggs < 260 GeV/c2 (95% C.L.) • CDF Run II goal : • MW~30 MeV/c2 • Mtop~2 GeV/c2

11. 佐藤・戸村・丸山・金　(筑波大） b l+ g q 100% t W+ n 15% 85% q t q g W- 100% q’ b Top Mass  l+jets Template Method Use dijet invariant mass for in-situ JES calibration. • New technique in Run II: Constrain the jet energy scale (JES) uncertainty by Wjj invariant mass in ttl+jets candidate events. • The obtained scale is applied to both b- and light-jets. • Fit is done in mtop vs JES plane. Likelihood countour: Reconstracted top mass (kinematic fit): World best single measurement: Mtop (template) = 173.4 ± 2.5 (stat. + JES) ± 1.3 (syst.) GeV(680 pb-1)

12. Top Mass Measurements Mtop~2 GeV/c2 achievable at L~2-3 fb-1 土屋・近藤　(早稲田大）　28日午後発表予定 DLM Method in dilepton channel Event reconstruction with Matrix Element calculation. 寄田　 (早稲田大、 現シカゴ大）

13. Top Mass Tevatron Combination • Correlation : • uncorrelated • stat. • fit method • in situ JetEnergyScale(JES) • 100% w/i exp(same period) • JES due to calorimeter • 100% w/i channel • bkgd. model • 100% w/i all • JES due to fragmentation, • signal model • MC generator Use only best analyses from each decay mode, each experiment.

14. Updated Electroweak Fit Results • New top mass world average : Mtop = 172.5  2.3 GeV/c2. • Updated preferred SM Higgs mass : • Mhiggs = 89 +42-30GeV/c2. • Mhiggs < 175 GeV/c2 (95% CL) . • < 207 GeV/c2 w/ LEP direct search limit. w/ Tevatron Run I average : Mtop = 178.0  2.7 3.3 GeV/c2 mhiggs=114 +69/-45 GeV/c2 mhiggs260 GeV/c2 (95% CL)

15. ttbar Resonance in Summer 2005 • Search for new massive resonance decaying to top pairs such as top-color Z’. • Using lepton+>=4jets (no-btag) sample. • Event reconstruction by assuming LO matrix element. • Constraint top mass = 175GeV/c2 • Fix SM backgrounds to expected rate • Use theory prediction of 6.7pb for SM top pair production Interesting excess, ~500GeV @ 319pb-1 (2005 summer)

16. Updated Search for ttbar Resonance • Same analysis was done using the 682pb-1!! • Same selection, same mass fitting. • Previous 318pb-1 data is a sub-sample of the full dataset. • Limit on a narrow vector resonance (GR=1.2% MR): • MR>725 GeV at 95%CL No significant excess

17. Top Lifetime • SM prediction : ttop~0.4x10-24 s • ttop<< 1/LQCD10-23 s  top does NOT hadronize (unique about top quark). • Measurement of ttop helps in confirming SM top assumption. • Measure lepton impact parameter (d0) in L+jets events with 1 b-tagged jets. • Use Zll to calibrate d0 resolution. Signal template

18. Top Lifetime Result (318 pb-1) Data prefers ttop=0. bkgd + signal(ttop=0) cttop < 52.5 mm (ttop <1.75x10-13 s) @ 95% C.L. First direct limit on top lifetime

19. Motivation for Single Top Search SM prediction: • Direct measurement of |Vtb|. • Unitarity of the CKM matrix. Is |Vtb| really ~1? • S-channel is sensitive to new resonance particles such as W’. Cross section is about half of ttbar. t-channel s-channel Vtb Vtb* Vtb* Vtb

20. Single Top Search Result (695 pb-1) Neural Net is trained for t- and s- channels, both combined and separately. B-tagger output is input to NN as well as event kinematic variables. • Bkgd categorized according to NN output shape: • Bottom-like = Wbb, WZ, ZZ, Z, non-W; Charm-like = Wcc, Wc, WW, mistag t+s combined NN output : Result of 2D NN fit : SM prediction • (t+s-chan.) = 0.8 +1.3-0.8 (stat) +0.2-0.3 (syst) pb • (t-chan.) < 3.1 pb @ 95% C.L. • (s-chan.) < 3.2 pb @ 95% C.L.  (t+s-chan.) < 3.4 pb @ 95% C.L.

21. Direct Search for SM Higgs Boson

22. SM Higgs Properties at Tevatron • Recent top mass measurement favors small Higgs mass. • Tevatron could compete with LHC if the Higgs is light. bb WW

23. 石澤　(筑波大、現triumph）、2006年夏 SM Higgs Search  WHlbb Event selection: • Isolated e/ w/ ET>20 GeV, ||<1. • Missing ET>20 GeV. • Two jets with ET>15 GeV, || < 2.0. • At least one jet is b-tagged. • Veto extra jets to reduce ttbar. • Total acceptance ~ 1.5% including Br[Wl]for mH=115.

24. SM Higgs Search  ZHbb Event selection: • Missing ET>70 GeV. • 2 jets w/ jet ET>25 GeV, ||<2.4. • Veto e/ w/ ET>10 GeV. • At least one jet is b-tagged. • Veto additional jets w/ ET>15 GeV. • Total acceptance ~ 3.6% including Br[Z]for mH=120.

25. SM Higgs Search  WW*ll • 2 opposite signed isolated e or . • 1st (2nd ) lepton w/ ET>20(10) GeV. • Veto jets to reduce ttbar bkgd. • missing ET>MH/4. • 16< mll< MH/2-5 GeV to reduce resonance. . • Total acceptance ~ 6% including Br[Wl]2 for mH=160. assuming mh~１60 GeV/c2

26. Summary of SM Search • The results are mostly ~1/2 years old. They will be updated very soon. 小林(筑波大）、2004年秋 95% exclusion upper limit SM prediction

27. Future Improvements on SM Higgs Search Luminosity Equivalent (s/b)2 Expect a factor of ~10 luminosity improvement per channel, and a factor of 2 from CDF+DØ Combination Start with existing channels, add in ideas with latest knowledge of how well they work (under studying) Analysis method will be improved with x2 dataset.

28. B Physics

29. BsBsOscillation Motivation md~|Vtd |2(BdBd Oscillation) constrains a side of unitarity triangle. By taking ratio md /ms we can rule out theoretical uncertainties and tighten the constraint on unitarity triangle. Orange band in the plot: the upper limit on |Vtd| is set by the lower limit of ms. Frequency ms~|Vts |2 from Dmd from Dmd/Dms Lower limit on Dms

30. BsBsOscillation Result (355 pb-1) Frequency scan, semileptonic and hadronic channels combined : • Oscillation not yet observed. • Frequency scan of the oscillation: • Fit for A for each ms. • A=1 for true ms. • Results will be updated very soon! • With double data (765 pb-1). • Newly developed same-side kaon flavor tagging will improve eD2 by a factor of ~3!! • Overall eD2=1.6% in current analyses. ms > 8.6 ps-1(95% CL limit)

31. b l+ w t w d, s l- w b l+ t Z/g w l- d, s Rare Decays Bs / Bd m+m- SM predictions on Branching Ratio : • SUSY may enhance the rate : • Event Selection (opposite sign di-muon) by likelihood discriminant composed with: • Isolation of tracks • Decay time • Direction of 2nd vtx and Pmm

32. 1 0 2 0 Observed : Bs / Bd m+m-Result (780 pb-1) central+central : central+forward : Likelihood Discriminant Likelihood Discriminant KK, K,  decays of Bd and Bs, with m-ID faked. World Best Limits!! BR( Bs → μμ ) < 1.0x10-7 @95% CL (2.6 x 10-6 in Run I ) BR( Bd → μμ ) < 3.0x10-8 @95% CL(8.6 x 10-7in Run I )

33. Bs Ds s s Bs Lifetime (360 pb-1) 魚住　(筑波大）　 30日午前発表予定 • Important input to Bs oscillation. • Use semi-leptonic decay : World second best value !!

34. M(Bc) = 6285.7 ± 5.3 ± 1.2 MeV/c2 (Bc )= 0.474 +0.073-0.066 ± 0.033 ps 青木　(筑波大）　 30日午前発表予定 e  b c c c Bc J/y - Bc Properties (360 pb-1) σ(Bc)BR(Bc→J/ψeν)/σ(B+)BR(B+→J/ψK+) = 0.282 ± 0.038 ± 0.074

35. Exotics

36. 秋元　(筑波大）　 28日午前発表予定 t VLQ3 b e or  jet ℓ ℓ  b  p p VLQ3 VLQ3 b   jet h 1 or 3 track(s) 3rd Generation Vector Leptoquark Search (322 pb-1) HT distributions for eh channels ( 2 jets) (h channel also analyzed.) VLQ M=320 s(pp  VLQ3 VLQ3) < 76 fb, mVLQ3 > 368 GeV/c2 (95% C.L.)

37. Summary • CDF Run II experiment is operating pretty well! • CDF has already collected ~1.3 fb-1 of data. • ~2.5 fb-1 by the end of 2006, ~8.5 fb-1 by 2009. • Many impressive results are being reported. • Many more results are already there! • Can not present everything in a limited time. • Please check www-cdf.fnal.gov for other results. • Important results are coming up/updating shortly, mostly with ~800 pb-1 dataset. Stay tuned!! • Update on direct Higgs search. • Update on Bs oscillation (measurement?). • 1st W mass measurement in Run II. • ……………..