Top Results at CDF Yen-Chu Chen/ 陳彥竹 中央研究院物理所 Institute of Physics, Academia Sinica Taiwan, ROC For the CDF collaboration ICFP /10/03-08

Yen-Chu Chen ICFP Outline The Top quark CDF experiment –Current (2005:1 fb -1 ) –Future (2009: 5 fb -1 up to 8 fb -1 or more) Top quark production Top quark mass measurement –Implication to Higgs search Search for resonance in t t pairs Future prospects Other Top physics Conclusion _

Yen-Chu Chen ICFP  The last of the 6 quarks.  Discovery was announced in 1995 by CDF and D0. The Top Quark

Yen-Chu Chen ICFP The Top quark Properties –Standard Model Charge : + 2/3 Spin : 1/2 Mass : ? → A free parameter in the model Higgs mass (m t, M W )

Yen-Chu Chen ICFP Top quark physics PP  t t  X b b  W  W  l  q l  q q' _ q' _ _ Production Cross section Top massTop polarization Decay modes, rare decays, etc. W helicity Top charge

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Yen-Chu Chen ICFP CDF detector

Yen-Chu Chen ICFP Integrated luminosity Stacking rate of the p. _

Yen-Chu Chen ICFP Data for Physics QCD Top Recorded 2002 → Aug Recorded: 530 pb -1 Physics: pb → Aug Recorded: 950 pb -1 Physics: 620 ~ 880 pb -1 Store Number (Aug.23,2005) Exceed 1 fb -1 recorded in Sep. 2005! 100 pb -1 in RUN I

Yen-Chu Chen ICFP Top quark production p p → t t   ~ 6.7 pb at √S = 1.96 TeV:  85% qq → t t  15% gg → t t _ _ _ _ _ _

Yen-Chu Chen ICFP t t decay modes Di-lepton: t t → W + bW – b → l + b l – b –Two high pt leptons, high missing energy, b-tagging Lepton + jet: t t → W + bW – b → l b qqb –One high pt lepton, high missing energy, b-tagging All jet: t t → W + bW – b → qqb qqb –b-tagging, number of jets, small missing energy, no high pt lepton, kinematical requirement, etc. _ _ _ _ _ _ _ _ _ _

Yen-Chu Chen ICFP Top di-lepton event candidate

Yen-Chu Chen ICFP  (t t ) di-lepton channel _

Yen-Chu Chen ICFP Number of events N top = L    is included in the MC  (tt) = 9.85 ± 2.13(stat) ± 1.30(sys) ± 0.5(lumi) pb Assuming m t = 178 GeV/c 2 _

Yen-Chu Chen ICFP Checking kinematics

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Yen-Chu Chen ICFP  (t t ) lepton+jet channel _

Yen-Chu Chen ICFP Needs b-tagging –Second vertex (SVX) tagging

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Yen-Chu Chen ICFP The result  = 8.7  0.9 (stat) (syst) pb –Assuming m t = 178 GeV/c 2  = 8.9  0.9 (stat) (syst) pb –Assuming m t = 175 GeV/c 2

Yen-Chu Chen ICFP Needs update

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Yen-Chu Chen ICFP Top mass

Yen-Chu Chen ICFP Top mass measurement - di-lepton - The challenges: – ’s not measured. –Combinatory of l + jet. Solutions: –Additional constraints –Matrix element –…

Yen-Chu Chen ICFP Top mass measurement - lepton-jet - Challenges: –Finding l + jet pair –b-jet tagging –Jet energy –… One of the solutions: –The W→j j mass was used as constraint. –Fit the Top mass and the jet energy scale (JES) simultaneously.  The world best Top mass measurement from single channel and single experiment: /-4.0 GeV/c 2

Yen-Chu Chen ICFP JES and top mass

Yen-Chu Chen ICFP m t = /-2.6  3.0 GeV/c 2

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Yen-Chu Chen ICFP SM Higgs mass = ?

Yen-Chu Chen ICFP Indication of new physics?

Yen-Chu Chen ICFP Search for X 0 → t t _

Yen-Chu Chen ICFP m (t t) _

Yen-Chu Chen ICFP Consistent with the SM?

Yen-Chu Chen ICFP Test the m(tt) spectrum with X 0 of various masses _

Yen-Chu Chen ICFP A fit with SM + X 0 (500)

Yen-Chu Chen ICFP Projection (  BR)

Yen-Chu Chen ICFP Projection (  m t ) Approaching 1.5 GeV uncertainty.

Yen-Chu Chen ICFP Projection (single Top) Single Top discovery could be next year!

Yen-Chu Chen ICFP More on Top properties W helicity in the Top decay –Current result supports the V-A theory. cos  and pt : –F0 = (stat. + syst.), F+ = (stat. + syst.) Mlb2: f(V+A) = F+ < 0.18 at 95% CL Br(t→Wb)/Br(t→Wq) = (stat) (sys) > 0.62 at 95% CL Br(t →  q)/Br SM (t →  q) < 5.0 at 95% CL Searching for charged Higgs in the Top decay Is it really Top? –Study on the Top charge in progress …

Yen-Chu Chen ICFP A bit more on Top charge Possibility –Q = – 4/3; true m t = GeV/c 2 Top charge study in progress More data on t t resonance _

Yen-Chu Chen ICFP Conclusion A lot of excitements will come out next year with 1 fb -1 or more data! The FNAL will run through 2009! Up to 8 fb -1 could be delivered! There could be more discoveries!

The best is yet to come!

Yen-Chu Chen ICFP BACKUP SLIDES

Yen-Chu Chen ICFP ILC at the FNAL?

Yen-Chu Chen ICFP Jet reconstruction

Yen-Chu Chen ICFP Second vertex (SVX) tagging –Long life time of the b quark Soft muon tagging –Semi-leptonic decay of the b quark b tagging

Yen-Chu Chen ICFP SVX b tagging

Yen-Chu Chen ICFP Single Top Top quark may also be produced as single   ~ 3 pb (t: 1.98  0.25; s: 0.88  0.11) t-channels-channel

Yen-Chu Chen ICFP Q  Q: charge of the lepton.  : pseudo- rapidity of the b jet.

Yen-Chu Chen ICFP Compared to data The non-top background includes: –miss tagged –W bb –W cc –W c –di-boson –non-W _ _

Yen-Chu Chen ICFP The M l b

Yen-Chu Chen ICFP Set upper limit: –t channel:  < 10.1 pb at 95% CL –s channel:  < 13.6 pb at 95% CL –combined:  < 17.8 pb at 95% CL  6.2 times higher than SM!

Yen-Chu Chen ICFP Projection of searching

Yen-Chu Chen ICFP Is it really Top? The “Top” quark discovered has a mass of 174 GeV or so, assuming SM. Can’t exclude the possibility of having a particle from SUSY model which could have a similar mass but with charge of – 4/3.

Yen-Chu Chen ICFP Top Charge

Yen-Chu Chen ICFP To obtain the Top charge - di-lepton - Jet charge calculation –Track quality –Jet track selection Jet charge cone size Min. and max. number of tracks in a jet Track p t –Jet charge formula Lepton-Jet pairing –M lb 2 pairing –Top mass as input

Yen-Chu Chen ICFP Charge of b jet: –Use jet charge to identify which jet is b and which one is b. –Soft lepton (muon) tagging. Calculate the charge sum of lepton and b in a pair. Count the difference between the |2/3| and |4/3| bins. _

Yen-Chu Chen ICFP Top charge study MC, signal Pythia 175 GeV, di-lepton, 2 jets only Top Q diff. between the |2/3| and |4/3| bins using 100 events. About 1  effect could be expected with 100 events.

Yen-Chu Chen ICFP Top charge study MC, background WZ, di-lepton, 2 jets only The WZ background has negligible effect on the Top charge. Top Q diff. between the |2/3| and |4/3| bins using 100 events.

Yen-Chu Chen ICFP Top charge estimation from - lepton + jet - Jet charge calculation –Similar to di-lepton case Lepton-Jet pairing –Top mass fitter Current study shows 3  effect could be achieved with 1fb -1 data.

Yen-Chu Chen ICFP W helicity in the Top decay W t l **  * is the angle between the charged lepton and the boost direction of W in the W rest frame from the Top rest frame. Due to V-A the polarization of W decay from the Top could be only longitudinal and left-handed. The branching fractions from the SM (longitudinal and right-handed): –F 0 = 0.7 (mt = 175 GeV/c2) –F + = 0.

Yen-Chu Chen ICFP F 0 = (stat.)  0.19 (syst.) F+ = 0.23  0.16 (stat.)  0.08 (syst.) From cos   2 M lb 2 cos  – ──── – 1 m t 2 – M w 2 

Yen-Chu Chen ICFP From lepton P T F 0 = (stat.)  0.17 (syst.) F+ = (stat.)  0.12 (syst.)

Yen-Chu Chen ICFP Combine both cos   and P T : –F0 = (stat. + syst.) –F+ = (stat. + syst.) The current results are consistent with the V-A !

Yen-Chu Chen ICFP W helicity from M lb 2 V-A and V+A predict different M lb 2 distritions. l+j single tag l+j double tag di-leptong

Yen-Chu Chen ICFP From RUN I data it appears that the fraction of V+A is consistent with 0! For RUN II with 2 fb-1 data, the expected uncertainty is 0.1 (stat.)  0.11 (sys).