1. Current Status of Top Quark Physics at ATLAS A. Onofre onofre@lipc.fis.uc.pt Jornadas LIP, Praia da Consolação, 21-22 Dezembro 2005

2. Current Status of Top Quark Physics at ATLAS 1) Mass measurement 2) Charge determination 3) Asymmetries in top decays and top spin correlations 4) W polarisation, A FB and New Angular Asymmetries 5) Rare decays of top quarks and FCNC 6) Single Top 7) Full Simulation @ Coimbra 8) Conclusions Outline

3. 1) Mass measurement M t (had) SN-ATLAS-2004-040 Sistematic Errors: Tot(sys) = 1.3 GeV Tot(stat) = 0.1 GeV protons W b t q q|q| quark Jet 2 Jet 1 Semileptonic Topology Semileptonic Topology pp tt bbW + W - (833pb) pp tt bbW + W - (833pb)

4. 2) Charge Determination Using the Semileptonic Topology Using the Semileptonic Topology Which one of these?  i q i (j.p i ) k  i (j.p i ) k Q b-jet = b-jet Conclusion: determination of b-quark charge (associated with l ± ) fixes top charge

5. 3) Asymmetries in top decays and top spin correlations Study top spin by looking to angular distributions of the decay products: Top Spin Correlations in pp tt: Top Spin Correlations in pp tt: h x = spin analysing power of particle x hxhxhxhx hxhxhxhx Top Spin Top Spin

6. The A j Asymmetry: The A lj Asymmetry: Semileptonic tt Events: The à lj Asymmetry: 3) Asymmetries in top decays and top spin correlations

7. ATLFAST (x=l, x´=j) _ (x=,x´=j) _ (x=l, x´=j) _ 3) Asymmetries in top decays and top spin correlations (L=10fb -1 ) For A lj : For à lj : For A j : N>0N>0 0>N0>N

8. ATLFAST Counting Experiments (2-bins) Similar Precision to Full Distribution Results Physics: Results: A xx´ =(A.h x.h x´ )/4 (A defined as in SN-ATLAS-2005-052) A=0.361±0.028(stat)±0.048(sys) (semileptonic channel only) For A lj For à lj For A j (L=10fb -1 ) 3) Asymmetries in top decays and top spin correlations

9. 4) W polarisation, A FB and New Angular Asymmetries t W 0 Longitudinal F 0 W b +1/2 0 W L Left F L t b W +1/2 -1/2 +1 W R Right F R t W b +1/2 +1 -1/2 V-A SUPRESSED The W has 3 helicity states: “Right”, “Longitudinal” and “Left” The top quark decay is the most important source of longitudinal Ws

10. 4) W polarisation, A FB and New Angular Asymmetries The Measurement of the W polarisation is a: Test of a SM Prediction: F 0 =0.7 e F L =0.3 (F R =0.0) Test of the tWb vertex structure: (V-A) F 0 =  0 /  t = 0.699±0.004(stat)±0.021(sys) F L =  L /  t = 0.299±0.004(stat)±0.019(sys) F R =  R /  t = 0.002±0.003(stat)±0.003(sys) cos(  lW )=-cos(  bl ) ATLAS (10fb -1 ): (semileptonic only) CDF

11. ATLFAST A FB =a 0 (F L -F R ) = 0.222 (LO) A - =a 1 F L -a 2 F 0 = 0.840 (LO) A + =-a 1 F R +a 2 F 0 =-0.549 (LO) The A FB, A + and A - Asymmetries Results (Counting Experiments): Definition of A FB, A + and A - : A FB = 0.223±0.004(stat)±0.013(sys) A + =-0.547±0.003(stat)±0.010(sys) A - = 0.839±0.002(stat)±0.003(sys) For A - For A + For A FB (F L,F R,F 0 defined as in SN-ATLAS-2005-052) (semileptonic channel only) 4) W polarisation, A FB and New Angular Asymmetries

12. ATLFAST Limits on the anomalous couplings: The A FB, A + and A - Asymmetries Anomalous couplings at the Wtb vertex: V R  [-0.10, 0.16] g L  [-0.08, 0.05] g R  [-0.02, 0.02] Phys.Rev.D67 (2003) 014009 (m b taken into account) (semileptonic channel only) (L=10fb -1 ) 4) W polarisation, A FB and New Angular Asymmetries

13. 5) Rare decays of top quarks and FCNC ● The top decays almost of the time through t  Wb [ B(t  Wb)~1 ] ● Top Rare Decays are Really Rare: B(t  Ws)<0.18%, B(t  Wd)<0.02% ● FCNC Top Decays: B(t   c) +B(t   u)<3.2% at 95% CL B(t  Zc) +B(t  Zu)<33% at 95% CL At 1-loop:

14. 5) Rare decays of top quarks and FCNC

15. A) ATLAS Sensitivity (5  ): B) Absence of Signal (95% C.L.): C) Dominant Systematic Errors: M t e  b-tag < 20%

16. 5) Rare decays of top quarks and FCNC Significant Gain in sensitivity with respect to present experimental data from CDF, LEP, and HERA

17. 6) Single Top Quark A) Single Top Production (SM): (  t-channel ~245pb;  s-channel ~5.1pb) (  t-channel ~245pb;  s-channel ~5.1pb) B) Associated Production (SM): (  ass ~31pb) (  ass ~31pb) C) FCNC Production (Beyond SM): (hep-ph/0510087 v2) (hep-ph/0510087 v2)

18. Signal: MC@NLO tt samples (e,μ) - AOD ref. T1 Full Simulation With EventView (to remove overlap between containers) 174860 events (120897 with weights) → ~0.6 fb -1 TopReX tt samples (e,μ) - AOD ref. 4520 and 4521 159274 events → ~1.3 fb -1 Background: MC@NLO tt samples (τ,ℓℓ) - AOD ref. T1 (as above) TopReX N non b jetsN b jets N leptons TopReX Single-t samples - AOD ref. 4511,4530,4531 and 4540 143636 events → ~37.7 fb -1 7) Full Simulation @ Coimbra

19. Full Simulation Comparison ATLFAST / MC@NLO / TopReX m W hadronic (GeV)m t leptonic (GeV) ATLFAST MC@NLO TopReX MC@NLO TopReX MC@NLO TopReX (L=0.3fb -1 ) (L=10fb -1 ) 7) Full Simulation @ Coimbra

20. Full Simulation at Coimbra 7) Full Simulation @ Coimbra A) Test in Standalone Machine (Pentium IV@2.6GHz, 512-RAM) Physics Channel: pp  tt  bWbW kB s B) Test in CENTOPEIA: 108 CPU´s (Pentium IV) Full ATLAS Simulation Software Installed (ATHENA) and running First Tests under way Results expected soon CFC/DF-UC

21. Conclusions b)The Asymmetry measurements are important tools to understand top-quark physics. They are sensitive to W polarisation, Top spin Correlations, New Couplings, etc. Counting experiments seam to work. c) Studies with full simulation under way Comparison ATLFAST - MC@NLO - TopReX d) and… 8) Conclusions a)Top-quark physics is getting momentum at ATLAS

22. 8) Conclusions e) Yes, you can spy on us… http://mars.fis.uc.pt/~atlas-top/index.shtml Updated Information on Outreach, people, presentations, meetings, publications, etc…

23. http://nautilus.fis.uc.pt/personal/top2006/ 8) Conclusions

24. http://nautilus.fis.uc.pt/personal/top2006/ 8) Conclusions f) Why not showing up at the top workshop?