Top: latest results from Tevatron

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Top latest results from Tevatron
cross-section and mass

• Mircea N. Coca
• University of Rochester, NY- CDF
• For the CDF and D0 collaborations
• FPCP 2003, Paris, June

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Outline

• Tevatron Status
• The upgrades of the CDF and D0 detectors
• Top Production and Decay
• Top Physics Program for Run II
• First Cross-Section Measurements at
• 1.96 TeV, in the Dilepton and Leptonjets
  channels
• Top Mass Measurements in CDF (Run II) and D0
  (Run I)
• Top Physics Prospects

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Tevatron Upgrades/Status

• Run II upgrades
• ECM increase from 1.8 ? 1.96 TeV?larger cross
  sections
• Higher luminosity
• Run I peak2.4x1031 cm-2 s-1
• Run II goal34x1032cm-2 s-1
• Run II peak4.7x1031 cm-2 s-1
• Analysis-quality data
• accumulated by Jan 03
• CDF 72.0 pb-1
• ( 57.5 pb-1 with silicon)
• D0 30 - 50 pb-1
• Immediate goal for accelerator
• Deliver 225 pb-1 in FY 2003
• Run IIa goal 2 fb-1

Integrated Luminosity
Winter 03
Commissioning
Peak Luminosity
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CDF and D0 Detectors Upgrades
D0
CDF

• Tracking
• Expanded silicon coverage
• New drift chamber (COT)
• Extended lepton-ID ?gt1.0 ?2.0
• End Plug calorimeter
• Expanded muon coverage

• New Inner tracking
• silicon tracker, fiber tracker
• 2T superconducting solenoid
• Upgraded ? system for better ? -ID

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Top Production and Decay
-

• In proton-antiproton collisions, at 1.96 TeV,
• top quarks are primarily produced in pairs
• single top production
• smaller rate (s 1.5 pb)
• large backgrounds
• not observed yet
• stt increased by 30 with the CM energy increase
  from 1.8 ?1.96 TeV
• Br(t?Wb) 100 in SM
• Based on the W decay modes ?3 experimental
  signatures

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85
-
(1) Dilepton Very small backgrounds, but very
small rate (2) LeptonJets Manageable
backgrounds and good rate (3) All Jets Large QCD
Background
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Top Physics in Run II
W helicity

• Run I discovery mode
• ( Fermilab 1995) ? crude look
• at tops properties
• Run II precision mode?
• we hope to answer fundamental
  questions
• Why is the top so heavy?
• Is the third
• generation special?
• Is top involved
• in EWSB?
• Is the top the liaison
• to new physics?

Top Mass
Top Width
l
Anomalous Couplings
Production cross-section
Top Spin
W
CP violation
Top Charge
Resonance production
p
n
t
b
Production kinematics
_
X
b
_
_
p
t
Top Spin Polarization
q
Rare/non SM Decays (eg t?Zc/gc, t?Hb)
W-
_
q
Branching Ratios
Vtb
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Production Cross-Sections

• measurement
• benchmark measurements
• test of perturbative QCD
• probe for physics beyond SM
• non-SM production, X ? tt
• non-SM decay, t ? Xb
• SUSY models with a tt-like signal
• Higgs production (WH,ZH) is a background
• and the opposite
• Run I
• Run IIa (2fb-1)
• Theoretical cross-section
• To estimate signal contribution we use 7 pb

Luminosity
Acceptance
dstt/stt 26
dstt/stt 7
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in the Dilepton Decay Mode
Backgrounds

• WW/WZ, Z/g? tt determined from Monte Carlo (MC)
• Z/g?ee, mm from dataMC
• Wjets, QCD Heavy Flavor from data

Event Selection
jet
jet

• 2 high-ET, isolated leptons (e, ?)
• t to be included for the future
• large missing energy ET
• D0 Raised ET cut in Z window
• CDF Veto Z-mass window events for ee, mm
• at least 2 jets with large ET
• large transverse energy flow
• HT ?(ETleptons ,ETjets)

l
l
b
b
n
n
p
p
p
p
b
b
E
E
l
l
T
T
jet
jet
n
n
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Dilepton Channel (ee, em, mm)
Run II Preliminary
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em2 jets Top Candidate
Transverse View
ET(e) 20.3 GeV pT(?-) 58.1
GeV/c ETjet(1) 141.0 GeV ETjet(2) 55.2
GeV ET 91 GeV HT (e)
216 GeV
ET
m-
jet
Longitudinal View
e
jet
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Dilepton Channel
Data sample luminosity 72 pb-1
Run II Preliminary
Events
DF(leptons)
Missing energy ET (GeV)
Missing energy ET (GeV)
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Kinematics of Dilepton Candidates
Run 1 L 109 pb-1 1.8 TeV 9 events
Run 2 Preliminary L 72 pb-1 1.96TeV 5 events

• Events with very large missing ET in Run 1

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LeptonJets
Event Pre-Selection

• A high PT isolated, charged lepton (e, m), large
  missing ET ( n undetected)
• Large jet multiplicity ( 3 )
• Cosmic ray, electron conversion removal, dilepton
  veto, Z boson veto.

Further selections to reduce the background
B-Jet with SECVTX

• topological
• 4 jets (DØ)
• b jets with Soft Lepton Tag (SLT)
• 3 jets, 1 SLT tag (DØ)
• b jets with displaced vertex (SECVTX)
• 3 jets, 1 b tag (CDF)

B-Jet with SLT
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LeptonJets Topological

• Backgrounds

• Event Pre-Selection

• Preselect a sample enriched in W events
• an EM object or m with large PT and large missing
  energy
• Veto soft ms in sample, veto dilepton events

• QCD multi-jets evaluated from data vs.Njets
• ejets due to fake jets (po and g)
• mjets due to heavy flavor decays
• W multi-jets background in the 4 jet bin
  estimated using data by Berends scaling law
  before topological cuts

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Results for Topological Analysis
Topological Selection
QCD background estimation

• 4 jets (h lt 2.5(m) or
• h lt 2.0(e), pT gt15 GeV)
• Aplanarity gt0.065
• HT(ETjets) gt180 GeV (e)
• HT(ETjetspTW)gt220GeV (m)

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LeptonJets with an SLT tag

• Event Selection

Backgrounds

• preselection as for topological stt
• 3 jets
• softer topological cuts
• HT(SETjets)gt 110 GeV
• Aplanarity gt 0.04
• soft m inside a jet
• (b?m, b?c?m)

• QCD and Wjets determined from data

Leptonjets channels (SLT Topological) combined
s
Run II Preliminary
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Leptonjets with a SECVTX-tag

• Event Selection

• preselect a sample enriched in W events as
  already mentioned
• 3 jets with ETgt15 GeV
• 1 jet with secondary vertex tag (SECVTX)

• A jet is tagged as b jet if it has at least 2
  good tracks and the displacement Lxy satisfies
  Lxy/?xy gt3 (typical ?xy150 ?m, while Lxy3 mm)

Probability of tagging a tt event
?(event tag) 45 ? 1 ? 5
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Backgrounds Estimation

• Backgrounds

Jet Multiplicity for the background events and
the data

• Mistags
• from tagged jets with Lxylt0 in inclusive jet
  data
• Wheavy flavor
• from Wjets data, b tag rate and flavor
  composition
• Non W
• from data
• WW, WZ, Z?tt, single top
• from Monte Carlo simulation

• 1 and 2 jet bins are used as a control sample,
  the top events are in gt 3 jet bins
• 15 Candidates in 57.5 pb-1

control
signal
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Leptonjets - SECVTX-tagging
Data sample luminosity 57.5 pb-1

Run II Preliminary
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A golden leptonjets candidate

• tt ljet candidate Nov 02 2002
• run 153693 event 799494
• ? 4 jets, with 2 SECVTX b-tags

SECVTX tag
Event primary vertex
SECVTX tag
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Top Cross-Sections Summary
D0 All channels combined Run II
Preliminary
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Top Mass Leptonjets
Event Selection
Reconstruction Method

• Select 4 jet events, similar to stt analysis,
  except no requirement for a jet to be b-tagged

• Each event?up to 24 solutions consistent with a
  top decay
• 12 different jet-partons assignments
• Every combination has two solutions for the n
  longitudinal momentum
• Impose MtMt , M(j,j)M(l,?)MW
• PDG MW, GW, Gt
• 2-C fit applied, chose the event top mass
  corresponding to the lowest ?? (iff ?? lt 10)
• Parameterized templates of top masses (150, 200)
  GeV and bkgd
• Continuous likelihood to extract top mass and
  statistical uncertainty

5 vertices 20 constraints
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Top Mass Measurement

• 33 candidates after event selection
• 8 events with a b tagged

Systematic uncertainty summary
CDF Run 1 combined Mtop 176.1 6.5 GeV/c2
Work to improve understanding of detector
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Top Mass using b-tagging

• Identifying a b-jet has a great impact
• Smaller combinatorics ? improves the mass
  resolution by 10
• Reduction in background?
• S/B 3, increase by 300
• Allow to loosen the 4th jet
• selection cuts ( 40 more events)
• In 57.5 pb -1 there are 11 candidates with at
  least one jet tagged as a b-jet
• Mtop with b-tagging is coming

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Run I Mass lepton4 jets events

• Similar with Kondos method, uses full set of
  event observables
• Define a signal event probability
• Define a background probability
• Build an event probability
• where a (Mt,c1,c2)
• Build a likelihood L(a), minimize lnL(a) to get
  c1, c2 and Mt

i-th event observables

• LO ME used, 4 jets required exclusively,
  additional cut on background
• probability (to improve the sample purity)

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Run I Preliminary result

• D0 Run I Statistics PRD 58(1998), 052001
• Events 91? 71 with exactly 4 jets ? 22 after
  probability cut

-log(likelihood) vs Mt
likelihood vs Mt
Stat 5.6 GeV from PRD 2001 improvement on the
statistical uncertainty (2.4? stats)
Run I D0 leptonjets 173.3 5.6(stat)  5.5 (syst
) GeV/c2
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Summary Conclusions

• Top physics is extremely rich and has a great
  potential
• Many top analyses are in progress
• we re-established the benchmark top quark
  measurements
• we are getting close to Run I precision
• Improvements are underway
• Better detector understanding
• Increase the tagging efficiencies of b jets
• Include forward leptons
• We are enthusiastic about the top physics
  prospects at the Tevatron until first LHC results
• Expect results from larger samples soon
• Many measurements will supersede those of Run I
• Test the Standard Model to even greater precision

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Top Physics Prospects for 2 fb-1
Measurement Est. Uncertainty
Tests Mt
2-3 GeV/c2 Indirect MH
dstt 7
QCD Couplings dsll/slj
12 Non-SM Decays
dB(t?Wb)/B(t?WX) 2.8
dB(t?Wb)/B(t?Xb)
9
dB(t?Wlong) 5.5
Non-SM Coup. dB(t?WVA)
2.7 W helicity
dsB(Z?t t)
90 fb Exotics
dstbXbtX
24 Observe single top
dG(t?Wb) 26
dVtb
13 CKM Matrix
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End of talk Backup Slides
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Top Mass Templates

• Reconstructed top masses from data are compared
  to parameterized templates of top and background
  Monte Carlo for masses (150, 200) GeV
• Use a continuous likelihood method to extract top
  mass and statistical uncertainty
• The bump in the background shape around 130 GeV
  is due to the kinematic selection of the events

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Top Dilepton Kinematics
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Constraint MHiggs with a Mtop and MW
DØ / CDF Run 2a Goal
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Direct Higgs Search
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Single Top