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RHUL-Royal Holloway, University of London: 16 th November 2007 Prospects of Top Quark Properties @ ATLAS A.Onofre (onofre@lipc.fis.uc.pt)
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Properties (T7 CSC Note+ST) Outline Top Mass Top Charge Top Spin and Spin Correlations Top t Wb decay tt Resonances Top FCNC decays Single Top FCNC Production Conclusions
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RHUL-Royal Holloway, University of London: 16 th November 2007 2 b-jets p T >20GeV ≥4 jets, R=0.4 p T >40GeV t(had) t(lep) W(had) Semileptonic Topology Dileptonic Topology e, b b W W 2 b-jets 2 leptons Studies done with tt Events Top Mass, Top Charge, Top Spin and Spin Correlations, Top t Wb decay and tt Resonances Correlations, Top t Wb decay and tt Resonances Top FCNC decays (t qX, X= g,Z,g) and Single-top
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Mass Many analyses performed in the past or being developed recently: Cut based Kinematic fit Template method, Matrix Element method, Analyses with soft muon b-tagging, high p T top, Analysis in leptonic final states with J/ y Correlation between lepton p T and m t
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Mass SACLAY Analysis: choice of light jet pair and in-situ re-calibration using a 2 fit to the PDG W mass Systematic uncertainties: Jet energy scale 1% on light jet 0.2 GeV/c 2 on m t 1% on b-jet 0.7 GeV/c 2 on m t ongoing ISR/FSR, b-quark fragm. Efficiency*3.44 ± 0.04% S/B100 ± 11 Purity63.8 ± 0.8 % 175.8 ± 0.4 GeV/c 2 FULLSIM (CSC) L=1fb -1 (SN-ATLAS-2004-040) L=10fb -1 ATLFAST (reminder) Tot(sys) = 1.3 GeV Tot(stat) = 0.1 GeV
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Charge Exotic t(-4/3) b(-1/3) W-W- l - (-1) nlnl SM t(2/3) b(-1/3) W+W+ l + (+1) nlnl SM (Q top =+2/3): Exotics (Q top = -4/3): Critical moment For top quark determination I) Determination of b-jet charge II) Correct (lepton, b-jet) pairing (Atlfast, PHYS-2003-35)
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Charge I) Determination of b-jet Charge: II) Correct (l ±, b) Pairing: m( l,b 2 ) m( l, b 1 ) M top =175 GeV A) Weighting Technique: B) Semileptonic Decay: Invariant mass criteria: Invariant mass criteria: b1b1 b2b2 l
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Charge (B.Zilka,S.Tokar) A) Weighting Technique: b b -0.0842 0.0044 0.0868 0.0043 0.0868 0.0043 ( Eff.=4.1% Purity: 89.3% ) L~0.5fb -1 B) Semileptonic Decay: (A. Tonoyan, E.Khramov) l+ l-
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Spin and Spin Correlations M tt <550 GeV A=0.42 Double Angular Distributions: M tt <550 GeV A D =-0.29 tt Spin Correlation Parameters: Although t and t not polarised in tt pairs, their spins are correlated (Zhu Chengguang)
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Spin and Spin Correlations Semileptonic + Dileptonic Syst (E b-jet,m top,FSR) 4-6% precision (Eur.Phys.J.C44S2 2005 13-33) L=10fb -1 ATLFAST (reminder) FULLSIM (CSC) L=1fb -1 Semileptonic Selection efficiency 2.9% (2.7% for Rome) Preliminary
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Spin and Spin Correlations Trigger Studies: Isolated single electron trigger Single muon trigger L=1fb -1 Results (Preliminary): Level of Precision of A, A D ~40%
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RHUL-Royal Holloway, University of London: 16 th November 2007 Spin Asymmetries can also be used: Error versus Luminosity: SM (LO): A lj =-0.0396 ( spin analysing power a l+ =1.0, a j =-0.51) A lj L=1fb -1 Level of Precision of A lj ~40% (Low MC) A lj ~30% (High MC) Top Spin and Spin Correlations
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RHUL-Royal Holloway, University of London: 16 th November 2007 t Wb Top Decays: 1) the t Wb decay By measuring the fraction of longitudinal W´s in top quark decays we are: V-A SUPPRESSED Testing a Standard Model prediction: F 0 =0.7 F L =0.3 Probing the structure of the Wtb vertex
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top t Wb decay (SM) Angular Distribution @ W c.m. How to measure the W Helicity Fractions? Using lepton angular distribution (with respect to top direction) in W cm system: SM(LO): F 0 =0.703, F L =0.297, F R =3.6x10 -4 (NLO): F 0 =0.695, F L =0.304, F R =0.001 cos( l *)
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RHUL-Royal Holloway, University of London: 16 th November 2007 (Eur.Phys.J.C44S2 2005 13-33) L=10fb -1 ATLFAST (reminder) Syst ( E b-jet,m top,FSR ) F 0 F 0 ~ 2% ; F R ~ 0.01 FULLSIM (CSC) L=1fb -1 Results (Preliminary) F 0 F 0 ~ 6% ; F R ~ 0.03 (Zhu Chengguang) Top t Wb decay (SM) (CDF) First Simultaneous fit:
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RHUL-Royal Holloway, University of London: 16 th November 2007 Anomalous Couplings @ the Wtb Vertex V R,g L,g R Change F 0,F L,F R How to Probe Anomalous Couplings? Extract Limits from F 0,F L and F R (and ratios) Fit angular distr. with V R, g L and g R (m b ≠0) Use Angular Asymmetries Eur.Phys.J. C50 (2007) 519-533 Top t Wb decay (BSM)
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RHUL-Royal Holloway, University of London: 16 th November 2007 Angular Asymmetries: (NLO): A FB =-0.2269, A + =0.5429, A - =-0.8402 (SM, LO): A FB =-0.2225, A + =0.5482, A - =-0.8397 Top t Wb decay (BSM)
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RHUL-Royal Holloway, University of London: 16 th November 2007 Anomalous Couplings Asymmetries (N. Castro) Error Versus Luminosity A+A+ A-A- Top t Wb decay (BSM) L~1fb -1 L=10fb -1
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RHUL-Royal Holloway, University of London: 16 th November 2007 Discovery Potential of a Narrow tt Resonance (E.Cogneras,D.Pallin) tt Resonances Discovery Potential: Window in mass spec. Compute the number of resonance events required for discovery: n X = 5 s deviation on n SM Semileptonic Resolution Current Limits:
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RHUL-Royal Holloway, University of London: 16 th November 2007 L=10fb -1 ATLFAST (reminder) Expected 95% CL Limits: Br(t qg) <1.3x10 -3 5 s Results: Br(t qZ) >4.4x10 -4 Br(t q g ) >9.4x10 -5 Br(t qg) >4.3x10 -3 (SN-ATLAS-2007-059) Top FCNC decays FCNC in tt Events tqZtqZtqgtqgtqgtqg
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RHUL-Royal Holloway, University of London: 16 th November 2007 FULLSIM L=1fb -1 Results Crucially Depend on Tagging Efficiencies (e, m, b, jets and g ) Likelihood Method works (need to have well defined shapes) Gluon Channel more difficult (F. Veloso) 5 s Results: Br(t qZ) ~ 10 -2 - 10 -3 Br(t q g ) ~ 10 -3 Br(t qg) ~ 10 -2 Top FCNC decays
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RHUL-Royal Holloway, University of London: 16 th November 2007 FULLSIM L=1fb -1 (F. Veloso) 5 s Results: Br(t q g ) ~ 10 -3 Top FCNC decays (w/o b-tag) Minimize c 2 by looping on jets (b,q=j1,j2) and scan on p Z to reconstruct kinematics
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RHUL-Royal Holloway, University of London: 16 th November 2007 FCNC in Single-t Production k qg =anomalous coupling =scale of new physics Event Selection: 1 lep ( p T >20GeV, <2.5 ) 1 b-jet ( p T >40GeV, <2.5 ) p T > 20GeV ( W and t p T, m bl, m T (W), H T, m t ) Systematics: signal (8%), b tag (6%), ISR (3.5%), PileUp (4%) Total ~ 12% Total ~ 12% e (ug)=1.08%, e (cg)=1.81% Back: W+j(80%), single-t(9%) L=10fb -1 ATLFAST (reminder) Results: (hep-ex/0702005) Br(t ug)~O(10 -3 ) Br(t cg)~O(10 -2 ) Estimate: “Direct” (T.L. Cheng, P.Teixeira Dias)
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RHUL-Royal Holloway, University of London: 16 th November 2007 The Direct Production is not the full Story FCNC in Single-t Production The gg qt Processes: The gq gt Processes: The X-section: Phys.Rev. D74 (2006) 014006 (R.Santos, P.Ferreira)
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RHUL-Royal Holloway, University of London: 16 th November 2007 FCNC in Single-t Production Just To Have an Idea of the Results for : 5 s and 95% CL Limits obtained L=10fb -1 5 s Discovery 95% CL Limit: 95% CL Limits: Br(t qg) ~O(10 -4 ) 5 s Discovery: Br(t qg) ~ O(10 -3 -10 -4 ) New Contributions Give Same Order of Magnitude Results as Direct Production Mechanism 1 Order of magnitude better than ttbar for the gluon channel
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RHUL-Royal Holloway, University of London: 16 th November 2007 Conclusions Atlas will perform precision studies in the top sector Several Methods Available to Extract Physical Observables Already @ 1fb -1 : Top Mass ~ O(few GeV/c 2 ) Top Charge (2/3 versus -4/3) > 5 s significance Spin Correlation Parameters (A,A D ) ~ 40% error Spin Asymmetries ~ 40% error W helicity fractions (F 0, F L, F R ) ~ 6%, ~10% and ~0.03 error Angular Asymmetries (A+,A-) ~ 3% and 1% error Anomalous Wtb Couplings (V R, g L, g R ) ~ 0.1, 0.05 and 0.03 error tt Resonances (1TeV) ~ ( ×Br) ≥ 8 pb FCNC top Decays (Br[t qX], X= g,Z,g) ~ 10 -2 - 10 -3
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RHUL-Royal Holloway, University of London: 16 th November 2007 Next Top Workshop (every 2 years) 2008
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RHUL-Royal Holloway, University of London: 16 th November 2007 Spare Slides
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RHUL-Royal Holloway, University of London: 16 th November 2007 Top Mass @ TEVATRON
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RHUL-Royal Holloway, University of London: 16 th November 2007 s tt @ TEVATRON
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