RHUL-Royal Holloway, University of London: 16 th November 2007 Prospects of Top Quark ATLAS A.Onofre

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

RHUL-Royal Holloway, University of London: 16 th November 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

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

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 % ± 0.4 GeV/c 2 FULLSIM (CSC) L=1fb -1 (SN-ATLAS ) L=10fb -1 ATLFAST (reminder) Tot(sys) = 1.3 GeV Tot(stat) = 0.1 GeV

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 )

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

RHUL-Royal Holloway, University of London: 16 th November 2007  Top Charge (B.Zilka,S.Tokar) A) Weighting Technique: b b    ( Eff.=4.1% Purity: 89.3% ) L~0.5fb -1 B) Semileptonic Decay: (A. Tonoyan, E.Khramov) l+ l-

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)

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.C44S ) L=10fb -1 ATLFAST (reminder) FULLSIM (CSC) L=1fb -1 Semileptonic Selection efficiency 2.9% (2.7% for Rome) Preliminary

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%

RHUL-Royal Holloway, University of London: 16 th November 2007 Spin Asymmetries can also be used: Error versus Luminosity: SM (LO): A lj = ( 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

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

RHUL-Royal Holloway, University of London: 16 th November 2007  Top t  Wb decay (SM) Angular 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 *)

RHUL-Royal Holloway, University of London: 16 th November 2007 (Eur.Phys.J.C44S ) 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:

RHUL-Royal Holloway, University of London: 16 th November 2007 Anomalous 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)  Top t  Wb decay (BSM)

RHUL-Royal Holloway, University of London: 16 th November 2007  Angular Asymmetries: (NLO): A FB = , A + =0.5429, A - = (SM, LO): A FB = , A + =0.5482, A - =  Top t  Wb decay (BSM)

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

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:

RHUL-Royal Holloway, University of London: 16 th November 2007 L=10fb -1 ATLFAST (reminder) Expected 95% CL Limits: Br(t  qg) <1.3x s Results: Br(t  qZ) >4.4x10 -4 Br(t  q g ) >9.4x10 -5 Br(t  qg) >4.3x10 -3 (SN-ATLAS )  Top FCNC decays FCNC in tt Events tqZtqZtqgtqgtqgtqg

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) ~ Br(t  q g ) ~ Br(t  qg) ~  Top FCNC decays

RHUL-Royal Holloway, University of London: 16 th November 2007 FULLSIM L=1fb -1 (F. Veloso) 5 s Results: Br(t  q g ) ~  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

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/ ) Br(t  ug)~O(10 -3 ) Br(t  cg)~O(10 -2 ) Estimate: “Direct” (T.L. Cheng, P.Teixeira Dias)

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) (R.Santos, P.Ferreira)

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( )  New Contributions Give Same Order of Magnitude Results as Direct Production Mechanism  1 Order of magnitude better than ttbar for the gluon channel

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  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) ~

RHUL-Royal Holloway, University of London: 16 th November 2007 Next Top Workshop (every 2 years) 2008

RHUL-Royal Holloway, University of London: 16 th November 2007 Spare Slides

RHUL-Royal Holloway, University of London: 16 th November 2007  Top TEVATRON

RHUL-Royal Holloway, University of London: 16 th November 2007  s TEVATRON