1. Prospect for Top Properties Measurement in Atlas
A.Onofre
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

2. Outline Top Properties Conclusions Top Mass Top Charge
Top Spin and Spin Correlations
Top tWb decay
Top FCNC decays
FCNC in Single-t Production
tt Resonances
Conclusions
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

3. Most of the Studies done with tt Events
Top Mass, Top Charge, Top Spin and Spin Correlations, Top tWb decay and tt Resonances
Semileptonic Topology
Dileptonic Topology
2 b-jets
pT>20GeV
≥4 jets,DR=0.4
pT>40GeV
t(had)
t(lep)
W(had)
e,m b W
2 b-jets
2 leptons
Top FCNC decays and FCNC in Single-t Production use different
analyses
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

4. Top Charge SM Exotic For top quark determination Critical moment
SM (Qtop=+2/3):
Exotics (Qtop= -4/3):
Exotic
t(-4/3)
b(-1/3) W-
l-(-1) nl SM
t(2/3)
b(-1/3) W+
l+(+1) nl
Critical moment
For top quark determination
I) Determination of b-jet charge
II) Correct (lepton, b-jet) pairing
(Atlfast, PHYS )
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

5. Top Charge I) Determination of b-jet Charge:
A) Weighting Technique:
B) Semileptonic Decay:
II) Correct (l±, b) Pairing:
1) Semileptonic Channel
2) Dileptonic Channel
Invariant mass criteria:
l and b2 from
different tops
l and b1 from
the same top
Mtop=175 GeV
( Cut optimized for mcr=145 GeV )
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

6. Top Charge A) Weighting Technique: B) Semileptonic Decay: b
(B.Zilka,S.Tokar)
A) Weighting Technique: b  
( Eff.=4.1% Purity: 89.3% )
L=1fb-1 l+ l-
B) Semileptonic Decay:
(A. Tonoyan)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

7. Top Spin and Spin Correlations
tt Spin Correlation Parameters:
Although t and t not polarised in tt pairs, their spins are correlated
(Zhu Chengguang)
Mtt<550 GeV
A=0.42
Double Angular Distributions:
Mtt<550 GeV
AD =-0.29
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

8. Top Spin and Spin Correlations
(Eur.Phys.J.C44S )
L=10fb-1
ATLFAST (reminder)
-0.29
0.42 SM
0.008 0.010 AD
0.014 0.023 A
Error (±stat ±syst)
Semileptonic + Dileptonic
Syst (Eb-jet,mtop,FSR)
4-6% precision
FULLSIM (CSC)
L=1fb-1
Preliminary
Semileptonic
Selection efficiency 2.9% (2.7% for rome)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

9. Top Spin and Spin Correlations
Trigger Studies:
Isolated single electron trigger
Single muon trigger
Results (Preliminary):
Level of Precision of A, AD ~40%
L=1fb-1
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

10. Top Spin and Spin Correlations
Spin Asymmetries can also be used:
(spin analysing power al+=1.0, aj=-0.51)
Error versus Luminosity:
Alj
SM (LO): Alj=
L=1fb-1
Level of Precision of Alj~40% (Low MC)
Alj~30% (High MC)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

11. Top Decays: 1) the tWb decay
By measuring the fraction of longitudinal W´s in top
quark decays we are:
Testing a Standard Model prediction: F0=0.7 FL=0.3
Probing the structure of the Wtb vertex
V-A SUPPRESSED
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

12. Top Decays: 1) the tWb decay
How to measure the W Helicity Fractions?
Using lepton angular distribution
(with respect to top direction)
in W cm system:
SM(LO): F0=0.703 , FL=0.297 , FR=3.6x10-4
(NLO): F0=0.695 , FL=0.304 , FR=0.001
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

13. Top Decays: 1) the tWb decay
(Eur.Phys.J.C44S )
L=10fb-1
ATLFAST (reminder)
Syst ( Eb-jet,mtop,FSR )
dF0/ F0 ~ 2% ; dFR ~ 0.01
FULLSIM (CSC)
L=1fb-1
Results (Preliminary)
dF0/ F0 ~ 6% ; dFR ~ 0.03
(Zhu Chengguang)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

14. Top Decays: 1) the tWb decay
Anomalous the Wtb Vertex
VR,gL,gR Change F0,FL,FR
Eur.Phys.J. C50 (2007)
How to Probe Anomalous Couplings?
Extract Limits from F0,FL and FR (and ratios)
Fit angular distr. with VR, gL and gR (mb≠0)
Use Angular Asymmetries
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

15. Top Decays: 1) the tWb decay
Angular Asymmetries:
(SM, LO): AFB= , A+= , A-=
(NLO): AFB= , A+= , A-=
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

16. Likelihood Distributions:
Top Decays: 1) the tWb decay
(SN-ATLAS )
ATLFAST (reminder)
L=10fb-1
(SM, LO)
FULLSIM (CSC)
L=1fb-1
Likelihood Distributions:
e+m e m
Three Different Samples:
e, m, e+m
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

17. Error Versus Luminosity
Top Decays: 1) the tWb decay
(N. Castro)
Asymmetries
Error Versus Luminosity
L~1fb-1 A+ A-
Anomalous Couplings
Flavour at the LHC Era
Yellow Report (in prep.)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

18. Br(tqX) in Several Models: FCNC Decays in tt Events
Top Decays: 2) Rare decays (FCNC)
Top FCNC Decays:
tqg
tqZ
tqg
Br(tqX) in Several Models:
Studied Decays:
FCNC Decays in tt Events
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

19. Top Decays: 2) Rare decays (FCNC)
In the absence of signal:
ATLFAST (reminder)
L=10fb-1
Current Limits:
Expected 95% CL Limits:
Br(tqg) <1.3x10-3
5s Results:
Br(tqZ) >4.4x10-4
Br(tqg) >9.4x10-5
Br(tqg) >4.3x10-3
(SN-ATLAS )
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

20. Top Decays: 2) Rare decays (FCNC)
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
5s Results:
Br(tqZ) ~
Br(tqg) ~ 10-3
Br(tqg) ~ 10-2
(F. Veloso)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

21. Back: W+j(80%), single-t(9%)
FCNC in Single-t Production
(T.L. Cheng)
“Direct”
L=10fb-1
ATLFAST (reminder)
kqg=anomalous coupling L =scale of new physics
Results:
Event Selection:
1 lep ( pT>20GeV, |h|<2.5 )
1 b-jet ( pT>40GeV, |h|<2.5 )
pT > 20GeV
( W and t pT, mbl, mT(W), HT, mt )
Systematics:
Dssignal (8%), btag (6%), ISR (3.5%),
PileUp (4%)
Total ~ 12%
e(ug)=1.08%, e(cg)=1.81%
Back: W+j(80%), single-t(9%)
(hep-ex/ )
Br(tug)~O(10-3)
Br(tcg)~O(10-2)
Estimate:
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

22. FCNC in Single-t Production
The Direct Production is not the full Story
The ggqt Processes:
Phys.Rev. D74 (2006)
The X-section:
The gqgt Processes:
The X-section:
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

23. Back:W+j(50%),t-chan(25%) tt(21%)
FCNC in Single-t Production
Just To Have an Idea of the Results:
New Contributions Included
in MC (TopReX 4.20)
Event Selection:
1 lep ( pT>30GeV, |h|<2.5 )
1 b-jet ( pT>50GeV, |h|<2.5 )
1 non b-jet ( pT>25GeV, |h|<2.5 )
pT > 25GeV
Likelihood Analysis
e(qg)=1.4%
Back:W+j(50%),t-chan(25%) tt(21%)
L=10fb-1
Very Preliminary
PT(W)
mlb
Cos(qn*)
Cos(ql)
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

24. FCNC in Single-t Production
Just To Have an Idea of the Results for :
L=10fb-1
5s and 95% CL Limits obtained
5s Discovery
95% CL Limit:
95% CL Limits:
Br(tqg) ~O(10-4)
5s 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
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC

25. Conclusions Already @ 1fb-1:
Atlas will allow to perform precision studies
Object Reconstruction (e, m, t, jets and g) Requires Care
Several Methods Available to Extract Physical Observables
1fb-1:
Top Charge (2/3 versus -4/3) > 5s significance
Spin Correlation Parameters (A,AD) ~ 40% error
Spin Asymmetries ~ 40% error
W helicity fractions (F0, FL, FR ) ~ 6%, ~10% and ~0.03 error
Angular Asymmetries (A+,A-) ~ 3% and 1% error
Anomalous Wtb Couplings (VR, gL, gR ) ~ 0.1, 0.05 and 0.03 error
FCNC top Decays (Br[tqX], X=g,Z,g) ~
Grenoble, 20 October 2007
Workshop on Top Physics : from the TeVatron to the LHC