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Current Status of Top Quark Physics at ATLAS

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

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Current Status of Top Quark Physics at ATLAS

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

  2. Current Status of Top Quark Physics at ATLAS Outline 1) Mass measurement2) Charge determination 3) Asymmetries in top decays and top spin correlations4) W polarisation, AFB and New Angular Asymmetries5) Rare decays of top quarks and FCNC6) Single Top7) Full Simulation @ Coimbra8) Conclusions

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

  4. b-jet Siqi(j.pi)k Qb-jet= Si(j.pi)k 2) Charge Determination Which one of these? b-jet Using the Semileptonic Topology Conclusion: determination of b-quark charge (associated with l±) fixes top charge

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

  6. Semileptonic tt Events: The Alj Asymmetry: The Ãlj Asymmetry: The Anj Asymmetry: 3) Asymmetries in top decays and top spin correlations

  7. 0>N N>0 For Alj: (L=10fb-1) _ _ (x=l, x´=j) (x=l, x´=j) For Ãlj: For Anj: _ (x=n,x´=j) 3) Asymmetries in top decays and top spin correlations ATLFAST

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

  9. WRRight FR W0Longitudinal F0 WL Left FL 0 +1 +1/2 +1/2 W W -1/2 t t +1/2 b b b t -1/2 +1/2 W +1 4) W polarisation, AFB and New Angular Asymmetries • The W has 3 helicity states: • “Right”, “Longitudinal” and “Left” • The top quark decay is the most important source of longitudinal Ws V-A SUPRESSED

  10. cos(qlW)=-cos(qbl) 4) W polarisation, AFB and New Angular Asymmetries • The Measurement of the W polarisation is a: • Test of a SM Prediction: F0=0.7 e FL=0.3 (FR=0.0) • Test of the tWb vertex structure: (V-A) CDF (semileptonic only) ATLAS (10fb-1): • F0 = G0/Gt = 0.699±0.004(stat)±0.021(sys)FL = GL/Gt = 0.299±0.004(stat)±0.019(sys) • FR = GR/Gt = 0.002±0.003(stat)±0.003(sys)

  11. 4) W polarisation, AFB and New Angular Asymmetries ATLFAST The AFB, A+ and A- Asymmetries For A+ For A- For AFB Definition of AFB, A+ and A-: Results (Counting Experiments): AFB=a0(FL-FR) = 0.222 (LO)A- =a1FL-a2F0= 0.840 (LO)A+ =-a1FR+a2F0=-0.549(LO) AFB= 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) (semileptonic channel only) (FL,FR,F0 defined as in SN-ATLAS-2005-052)

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

  13. FCNC Top Decays:B(t gc) +B(t gu)<3.2% at 95% CL B(t Zc) +B(t Zu)<33% at 95% CL 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% At 1-loop:

  14. 5) Rare decays of top quarks and FCNC

  15. 5) Rare decays of top quarks and FCNC A) ATLAS Sensitivity (5s): B) Absence of Signal (95% C.L.): C) Dominant Systematic Errors: Mt e eb-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): B) Associated Production (SM): (sass ~31pb) (st-channel ~245pb; ss-channel~5.1pb) C) FCNC Production (Beyond SM): (hep-ph/0510087 v2)

  18. N non b jets N b jets N leptons TopReX TopReX TopReX 7) Full Simulation @ Coimbra Full Simulation With EventView (to remove overlap between containers) Signal: MC@NLO tt samples (e,μ) - AOD ref. T1 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 Single-t samples - AOD ref. 4511,4530,4531 and 4540 143636 events → ~37.7 fb-1

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

  20. A) Test in Standalone Machine (Pentium IV@2.6GHz, 512-RAM) Physics Channel: ppttbWbW s kB 7) Full Simulation @ Coimbra Full Simulation at Coimbra • 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. 8) Conclusions Conclusions a)Top-quark physics is getting momentum at ATLAS 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…

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

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

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

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