current status of top quark physics at atlas
DESCRIPTION
A. Onofre [email protected]. 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. - PowerPoint PPT PresentationTRANSCRIPT
Current Status of Top Quark Physics at ATLAS
A. Onofre
Jornadas LIP, Praia da Consolação, 21-22 Dezembro 2005
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, AFB and New Angular
Asymmetries
5) Rare decays of top quarks and FCNC
6) Single Top
7) Full Simulation @ Coimbra
8) Conclusions
Outline
1) Mass measurement
MMtt(had)(had)
SN-ATLAS-2004-040
Sistematic Errors:Sistematic Errors:
Tot(sys) = 1.3 GeVTot(stat) = 0.1 GeV
protons protons
W b
t
qq|
quark
quark Jet 2
Jet 1
Semileptonic Semileptonic TopologyTopology
pp tt bbWpp tt bbW++WW-- (833pb) (833pb)
2) Charge Determination
Using the Using the Semileptonic Semileptonic TopologyTopology
Which one of these?
iqi(j.pi)k
i(j.pi)kQb-jet=
b-jet
b-jet
Conclusion: determination of b-quark charge (associated with l±) fixes top charge
3) Asymmetries in top decays and top spin correlations
Study Study top spintop spin by looking to angular by looking to angular distributions of the decay products:distributions of the decay products:
Top Top Spin Correlations in pp Spin Correlations in pp tt: tt:
hhxx = spin analysing power of particle x = spin analysing power of particle x
hhxx
hhxx
Top Top SpinSpin
The Aj Asymmetry:
The Alj Asymmetry:Semileptonic tt Events:
The Ãlj Asymmetry:
3) Asymmetries in top decays and top spin correlations
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 Alj:
For Ãlj:
For Aj:
N>0
0>N
ATLFAST Counting Experiments (2-bins)
Similar Precision to Full Distribution Results
Physics:
Results:
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)
For Alj
For Ãlj
For Aj
(L=10fb-1)
3) Asymmetries in top decays and top spin correlations
4) W polarisation, AFB and New Angular Asymmetries
t
W0 Longitudinal
F0
W
b
+1/2
+1/2
0
WL Left
FL
tb
W
+1/2
-1/2
+1
WR Right
FR
tW
b
+1/2+1
-1/2V-A
SUPRESSED
The W has 3 helicity states: “Right”, “Longitudinal” and “Left”The top quark decay is the most important source of longitudinal Ws
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)
F0 0.890.340.30 (stat)0.17(syst)
F0 0.25@95%CLF0 = 0/t = 0.699±0.004(stat)
±0.021(sys) FL = L/t = 0.299±0.004(stat)±0.019(sys) FR = R/t = 0.002±0.003(stat)±0.003(sys)
cos(lW)=-cos(bl)
ATLAS (10fb-1): (semileptonic only)
CDF
ATLFAST
AFB=a0(FL-FR) = 0.222 (LO)
A- =a1FL-a2F0 = 0.840 (LO)
A+ =-a1FR+a2F0=-0.549
(LO)
The AFB, A+ and A- Asymmetries
Results (Counting Experiments):
Definition of AFB, A+ and A-: 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)
For A-
For A+
For AFB
(FL,FR,F0 defined as in SN-ATLAS-2005-052)(semileptonic channel only)
4) W polarisation, AFB and New Angular Asymmetries
ATLFAST
Limits on the anomalous couplings:
The AFB, A+ and A- AsymmetriesAnomalous couplings at the Wtb
vertex:
VR [-0.10 , 0.16]
gL [-0.08 , 0.05]
gR [-0.02 , 0.02]
Phys.Rev.D67 (2003) 014009(mb taken into
account)
(semileptonic channel only)
(L=10fb-
1)
4) W polarisation, AFB and New Angular Asymmetries
5) Rare decays of top quarks and FCNC
● The top decays almost of the time through tWb [ B(tWb)~1 ]
● Top Rare Decays are Really Rare: B(tWs)<0.18%, B(tWd)<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:At 1-loop:
5) Rare decays of top quarks and FCNC
5) Rare decays of top quarks and FCNC
A) ATLAS Sensitivity (5A) ATLAS Sensitivity (5):):
B) Absence of Signal (95% C.L.):B) Absence of Signal (95% C.L.):
C) Dominant Systematic Errors: MC) Dominant Systematic Errors: Mtt e e b-tagb-tag < < 20%20%
5) Rare decays of top quarks and FCNC
Significant Gain Significant Gain in sensitivity in sensitivity
with respect to with respect to present present
experimental experimental data from CDF, data from CDF, LEP, and HERALEP, and HERA
6) Single Top Quark
A) Single Top Production A) Single Top Production (SM):(SM):
((t-channel t-channel ~245pb; ~245pb; s-channels-channel~5.1pb)~5.1pb)
B) Associated Production B) Associated Production (SM):(SM):
((assass ~31pb) ~31pb)
C) FCNC Production (Beyond SM):C) FCNC Production (Beyond SM):
(hep-ph/0510087 v2)(hep-ph/0510087 v2)
Signal: MC@NLO tt samples (e,μ) - AOD ref. T1
Full SimulationWith EventView (to remove overlap between containers)
174860 events (120897 with weights) → ~0.6 fb-1
TopReX tt samples (e,μ) - AOD ref. 4520 and 4521159274 events → ~1.3 fb-1
Background: MC@NLO tt samples (τ,ℓℓ) - AOD ref. T1 (as above)
TopReX TopReX TopReX
N non b jets N 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
Full SimulationComparison ATLFAST / MC@NLO / TopReX
mW hadronic (GeV)
mt leptonic (GeV) mt leptonic (GeV)
ATLFAST ATLFAST ATLFAST
MC@NLOTopReX
MC@NLOTopReX
MC@NLOTopReX
(L=0.3fb-1) (L=0.3fb-1) (L=0.3fb-1)
(L=10fb-1) (L=10fb-1) (L=10fb-1)
7) Full Simulation @ Coimbra
Full Simulation at Coimbra
7) Full Simulation @ Coimbra
A) Test in Standalone Machine (Pentium [email protected], 512-RAM) Physics Channel: ppttbWbW
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
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
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…
http://nautilus.fis.uc.pt/personal/top2006/
8) Conclusions
http://nautilus.fis.uc.pt/personal/top2006/8) Conclusions
f) Why not showing up at the top workshop?