The Top Quark Beyond the SM at ATLAS

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The Top Quark Beyond the SM at ATLAS
António Onofre LIP / UCP
Universidad de Granada Departamento de Física
Teórica y del Cosmos
Granada 29th June 2006
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Outline
I) What do we know about the top
quark? II) The top quark at ATLAS III)
Conclusions
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I) What do we know about the top quark?
From the SM we know that

• The top quark completes the 3 family structure of
  the SM
• It has spin1/2,
• Charge2/3,
• Its the weak-isospin partner of the b-quark,
• G1.42GeV (including mb,MW,as,EW corr.)
• Its a massive particle (special role in SM?)

N? 2.98410.0083
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I) What do we know about the top quark?
Beyond SM
Beyond SM
SMBeyond
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I) What do we know about the top quark?
The present experimental knowledge on top quark
physics is dominated by the TEVATRON data
The TEVATRON

• Run I (1992-1996)
• ?s 1.8 TeV
• Discover top quark in 1995
• Integrated luminosity 120pb-1
• Run II (2001-present)
• ?s 1.96 TeV
• Total Int.Luminosity Delivered 1.5fb-1/exp
• Recorded 1.2fb-1/exp
• Futur 2fb-1 (by 2006)
• 4fb-1 (by 2007)
• 8fb-1 (by 2009)
• 2 multi-purpose detectors
• D? and CDF

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I) What do we know about the top quark?
A) The top mass (TEVATRON,LEP,SLD)
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I) What do we know about the top quark?
A) The top mass at RUN II (TEVATRON)
Summary of Top Mass Results
mt172.52.3 GeV/c2
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I) What do we know about the top quark?
Diagrams
Dependence with Energy
Top quarks are rare events 1 in 1010 events !!!
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I) What do we know about the top quark?
CDF Run 2 Preliminary
D0 RUN 2 Preliminary
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I) What do we know about the top quark?

• W boson has three helicity states
• Left-handed, Longitudinal, Right-handed
• Top quark decay is the most significant
• source of Longitudinal Ws.

V-A SUPPRESSED
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I) What do we know about the top quark?

• By measuring the fraction of longitudinal Ws we
  are
• Testing a Standard Model prediction F00.7
  F-0.3
• Probing the structure of the tWb vertex

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I) What do we know about the top quark?
D) Top Rare decays

• The top quark almost always decays to a b quark,
  B(t?Wb)1
• Most of the SM rare decays of the top are really
  rare
• B(t?Ws)lt0.18, B(t?Wd)lt0.02

• The Ratio of Events with b-tagged and no b-tagged
  jets is
• RB(t?Wb)/B(t?Wq) Vtb2 / (Vtd2
  Vts2 Vtb2) 99.8

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II) The top quark at ATLAS
Why Going Beyond the SM?
A) The Most Exciting Discoveries are the
Unexpected Ones Unfortunately it Seems
Difficult To Predict the Unexpected
B) Physics Beyond the SM Required for
Unification SuperSymetry at TeV scale
modifies evolution of couplings ?
Unification and Agreement with Data
C) New Physics is also a test of the SM It is
mandatory to measure the top quark quantum numbers
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II) The top quark at ATLAS
ATLAS at CERN
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II) The top quark at ATLAS
ATLAS at CERN
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II) The top quark at ATLAS
Cross-sections at the LHC

• High Collision Rate
• LHC (Tevatron) every 25ns (396ns)
• High Cross-Sections 0.1b
• 2-3 interactions per collision
• LHC low/high lumi L1033cm-2s-1
• 20 interactions per collision
• LHC design/high lumi L1034cm-2s-1
• W, Z, top are rare events
• Requires High Luminosity
• Trigger is crucial sel. Leptons High pT

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II) The top quark at ATLAS
A) The top mass at ATLAS
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II) The top quark at ATLAS
A) The top mass at ATLAS

• Selected 87000 events for 10fb-1 (S/B78)
• Most Important Systematic Errors
• Energy Jet Calibration
• FSR

SN-ATLAS-2004-040
Systematic Errors
Tot(sys) 1.3 GeV Tot(stat) 0.1 GeV
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay
Angular Asymmetries AFB, A and A-
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay

• Pre-Selection (Probabilistic)
• 1 lepton pTgt25GeV,hlt2.5
• ?4 jets, pTgt20GeV,hlt2.5
• 2 b-tag jets
• Missing pTgt20GeV
• Final Selection
• Log10(Ls/LB) gt -0.2

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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay

• The measured Angular Distributions are affected
  by detector related effects (resolutions,
  triggers, selection criteria, etc.)
• To recover the True signal (S) Angular
  Distributions, reference MC samples for signal
  (Sref) and back. (Bref) were generated to
  estimate the expected Correction Function used to
  compensate for experimental effects (fCG/Sref)
• The signal is extracted from Data (S0B0) by

S (S0 B0 - Bref) x G/Sref
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay
Systematic Errors

• SM (LO)
• AFB -0.2226
• A 0.5482
• A- -0.8397

s/AFB 6.0 s/A 1.9 s/A- 0.4
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay
The dependence of AFB on the Anomalous Couplings
The b-quark mass must be taken into account
(differences up to 17 in gL and 9 in VR)
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay
1) Anomalous Couplings with W polarization
(careful with definitions when comparing to
TEVATRON)
2) The helicity fractions are related to AFB, A
and A-
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II) The top quark at ATLAS
B) Anomalous Couplings in the t?bW decay
Working Going on
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
Highly Suppressed in the SM
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
Pre-Selection
Probabilistic Type of Analysis after
Pre-selection
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
Specific Criteria
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
Specific Criteria
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
Specific Criteria
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
A) ATLAS Sensitivity (5s)
B) Absence of Signal (95 C.L.)
C) Dominant Systematic Errors Mt e eb-tag lt 20
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II) The top quark at ATLAS
C) Top Quark FCNC decays (tt events)
Combined Plot
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Conclusions

• There is no doubt that colliders are doing a
  Great Job up to now

• Many analysis are under preparation for the LHC
  and a strong collaboration between Theoreticians
  and Experimentalists is necessary

• The Top Quark Physics is one of the best places
  to look for New Physics (at least it is there)

Wait for the next data at the LHC...
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II) The top quark at ATLAS
B) Top spin correlations (asymmetries)
ai analysing power of particle i
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II) The top quark at ATLAS
B) Top spin correlations (asymmetries)

• Double Differential Distributions

• Opening Angle Distributions

• SM Predictions

• Asymmetries Definitions

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II) The top quark at ATLAS
B) Top spin correlations (asymmetries)
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II) The top quark at ATLAS
B) Top spin correlations (asymmetries)
Systematic Errors (probabilistic)
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II) The top quark at ATLAS
E) Top Quark FCNC decays (Single top Events)
A) Diagrams For Single top production
B) Decays under study
e
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II) The top quark at ATLAS
E) Top Quark FCNC decays (Single top Events)
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II) The top quark at ATLAS
E) Top Quark FCNC decays (Single top Events)
A) ATLAS Sensitivity (5s)
B) Absence of Signal (95 C.L.)
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New InteractionsQuark Radius at Colliders

• HERA (H1)
• Results Interpreted in terms of fq(Q2)

ds/dQ2 dsSM/dQ2 x fq(Q2)
q-form factor
Result Rlt1.7x10-16cm

• Tevatron (CDF, DY ee-,mm-)
• Result Rlt1.0x10-16cm

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• In SM (mt175GeV/c2)
• B(t g c) 5.2x10 -13
• B(t Zc) 1.5x10 -13
• SM extensions lead to large enhancements
• 1). 2HDM Þ gij a (mqimqj)
• 2). kg, kZ
• CDF searched for
• tg c(u) and tZc(u)
• B(tg c) B(tg u) lt 3,2
• B(tZc) B(tZu) lt 33

• CDF Þ k2g lt0.176
• k2Zlt0.533 at Lmt
• At LEP
• kg, kZ are
  Anomalous Couplings

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• DELPHI, OPAL, L3, ALEPH
• searched at LEP for
• ee- tc(u) bWc(u)
• Hadronic Wqq
• Leptonic Wln