CDF
Results for Top and Higgs at Tevatron
Outline
Tevatron
CDF and DØ
Top quark studies
Search for Higgs
Summary
ICHEP 2004, August 16-22, Beijing China
Dmitri Denisov, Fermilab
CDF
Top Quark Studies and Higgs Searches
Discovery of top quark at Fermilab in 1995
Completed SM Quark Sector
Studies of heaviest known elementary particle
SM parameters, tests
Beyond SM searches
Higgs boson is last missing particle in SM
Describes EWSM – particle masses
Experimental challenges: low cross sections and
substantial backgrounds
Accelerator
Detectors
Analysis
Tevatron currently is the only accelerator able to
produce such heavy particles
Dmitri Denisov, ICHEP04, August 21 2004
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Tevatron Parameters
CDF
Substantial upgrades for Run II: 2001-2009
10% energy increase: 30% higher stop
integrated luminosity increase: x50
Run I
Run IIa
Run IIb
66
36  36
36 36
1.8
1.96
1.96
1.6 1030
9 1031
3 1032
 Ldt (pb-1/week)
3
17
50
Bunch crossing (ns)
3500
396
396
2.5
2.3
8
Bunches in Turn
s (TeV)
Typical L (cm-2s-1)
Interactions/ crossing
Run I  Run IIa  Run IIb
0.1 fb-1
Dmitri Denisov, ICHEP04, August 21 2004
6 km long Tevatron ring
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CDF
Tevatron Run II Performance
1.1032 cm-2sec-1
0.7 fb-1
1 week=168 hours
Peak luminosity is above 1.1032 cm-2sec-1
Reliable operation
 in stores ~120 hours/week
Total ~0.7 fb-1 delivered in Run II
 as planned
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Tevatron Long Term Luminosity Plan
To reach higher masses with the same energy
 higher luminosity
Increase in number of antiprotons
 the key for higher luminosity
Expected peak luminosity
 3.1032 cm-2sec-1 by 2007
Today
Dmitri Denisov, ICHEP04, August 21 2004
Currently expecting delivered
luminosity to each experiment
 4-8 fb-1
by the end of 2009
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CDF
CDF and DØ Experiments in Run II
CDF
New Silicon Detector
New Central Drift Chamber
New End Plug Calorimetry
Extended muon coverage
New electronics
DØ
Silicon Detector
2 T solenoid and central fiber tracker
Substantially upgraded muon system
New electronics
Driven by physics goals detectors are becoming “similar”:
silicon, central magnetic field, hermetic calorimetry and muon systems
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Data Collection by Experiments
CDF and D0 experiments are very complex
Typical ratio of “recorded” to “delivered”
luminosity is 80%-90%
As of now both experiments recorded ~0.5 fb-1
Results presented correspond to ~0.2 fb-1
CDF
Analyzed data
Analyzed data
Dmitri Denisov, ICHEP04, August 21 2004
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Detection of High Pt Objects
CDF
Electrons
Muons
Missing Et
Jets
Top and Higgs final decay
products
 electrons
 muons
 jets (b)
 missing Et (n)
Detection and MC
optimization using well
known objects
D0 Preliminary
b tagging
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Top Quark Studies
Heaviest known elementary particle: 180GeV
 measure properties of least known quark
 top quark mass constrains Higgs mass
 sensitive to new physics
 short life time: probe bare quark
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Top Quark Production and Decays
Decay
Production
In SM top decays 100% to Wb
Classification of top decays
is based on Ws decays
Top quarks at Tevatron are (mainly)
produced in pairs via strong interaction
85%
15%
%
en
n
n
qq
en
1.2
2.5
2.5
14.8
1.2
2.5
14.8
1.2
14.8
n
Top pair cross section at 1.96 TeV is 6.7 pb
n
qq
44.4
Top decays classification: di-lepton, lepton+jets, all jets
Dmitri Denisov, ICHEP04, August 21 2004
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Selection of Top Quark Events
CDF
“Di-lepton” mode has
In triggering and analysis
select events with




high Pt leptons
high Et multiple jets
large missing Et (n)
displaced vertex for b jets
Dmitri Denisov, ICHEP04, August 21 2004
 low backgrounds: di-bosons, Drell-Yan, ...
 but low statistics: ~5% for e,  decays
“Lepton+jets” very productive mode
 6 times more decays then di-lepton mode
 main background W+jets
 good purity after b tagging
“All jets” mode
 ~50% branching
 high QCD backgrounds, jets combinatoric
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CDF
DØ Top Cross Section in di-lepton Channel
Topological selection
 isolated (not in jet) high Pt ee(156 pb-1),
(140 pb-1), e(143 pb-1) pair
 2 or more jets
 large missing Et
Backgrounds: WW, Z+jets, W+jets, fakes
D0 Run II Preliminary
s (tt )  14.354..13 ( stat ) 12..96 ( syst ) pb
Ultra-pure sample of top events: S/N>50
Cross Section
e only
Extra b tag
Dmitri Denisov, ICHEP04, August 21 2004
s (tt )  11.154..83 ( stat ) 11..44 ( syst ) pb
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CDF
CDF Top Cross Section in di-lepton Channel
197 pb-1 data sample for all channels
 topological selection
Combine ee,  and e channels for best
precision
pb
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
CDF Top Cross Section in lepton+jets Channel
l+jets topological
l+jets with vertex b tagging
s (tt )  5.6 11..02 ( stat) 10..07 ( syst ) pb
s (tt )  6.7 11..11 ( stat ) 11..66 ( syst ) pb
l+jets with soft lepton tagging
Exploit different strategies
 higher statistics – topological
 b-jets tagging
 displaced vertex
 soft lepton ()
Dmitri Denisov, ICHEP04, August 21 2004
s (tt )  4.2 12..99 ( stat ) 11..44 ( syst ) pb
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CDF
DØ Top Cross Section in lepton+jets Channel
Selection of events (topological method)
 high Pt lepton
 large missing Et
 4 or more jets (no b tagging)
Form topological discriminant to optimize
top events selection
s (tt )  7.2 22..64 ( stat) 11..76 ( syst ) pb
Single b tag
Double b tag
Tagging jets from b decays using
displaced vertex algorithms
reduces backgrounds substantially
s (tt )  8.2 11..33 ( stat ) 11..69 ( syst ) pb
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Run II Top Quark Cross Section: Summary
Errors between different channels are correlated
Measurements demonstrate success of multiple top detection techniques
Results within errors consistent with NNLO SM predictions for 1.96TeV of 6.7pb
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Top Quark Mass Measurement
Fundamental SM parameter
Top mass together with EW data constrain Higgs mass
Using Run I l+jets events (125 pb-1) DØ developed “matrix element method”
Detailed knowledge of top quark decay and detector response is required
 event by event likelihood calculated vs mt
Phase space x LO ME
PDFs
Probability for
observable x when y
was produced (Ex:
quark ET  jet ET)
Currently single most precise top mass
measurement
mt = 180.13.6(stat)3.9(syst) GeV
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Run II Top Mass Measurement at CDF
Run I style “template” method is efficiently used
di-leptons
l+jets, b tagged
17.2
mt  176.516
.0 ( stat )  6.9( syst ) GeV
mt  174.9 77..17 ( stat )  6.5( syst ) GeV
l+jets, multivariate
mt  179.6 66..43 ( stat )  6.8( syst ) GeV
Dynamical Likelihood Method is similar to D0 “matrix element method”
mt  177.845..50 ( stat )  6.2( syst ) GeV
Dmitri Denisov, ICHEP04, August 21 2004
Single most precise Run II measurement
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CDF
Top Quark Mass Measurement at DØ in Run II
Measurements in l+jets channel (~150 pb-1)
 template method uses templates for signal and background mass spectra
 ideogram method uses analytical likelihood for event to be signal or
background
Template
Ideogram
Template method mt = 1706.5(stat)+10.2/-5.7(syst) GeV
Ideogram method mt = 177.55.8(stat)7.1(syst) GeV
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Tevatron Top Quark Mass Measurement
New combined Run I result
(Was mt = 174.35.1 GeV)

mt = 178.04.3 GeV
Run II top quark mass results from both detectors are available
Systematic error
(mainly jet energy scale)
is becoming limiting accuracy
factor
TeV EWWG is working on combining Run II top mass measurement from CDF and DØ
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Search for Single Top Quark Production
EW production of top quark
 direct probe of |Vtb|
 search for new physics
Events selection: is similar to top pairs in l+jets mode, but with lower jets multiplicity
 backgrounds (W+jets, tt, di-bosons) are substantial
Need above 1 fb-1
for observation
95% C.L. limits
CDF
DØ
s (s-channel)
<13.6pb
<19pb
s (t-channel)
<10.1pb
<25pb
s (s+t channels)
<17.8pb
<23pb
Dmitri Denisov, ICHEP04, August 21 2004
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Unexpected Top Quark Decay Modes?
CDF
Assuming three-generation CKM matrix unitarity, |Vtb|~1.0
R = BR(tWb)/BR(tWq) ~1.0
Can measure ratio by checking the b quark content of the top sample decay products
If efficiency to tag a b quark is eb (~0.45 at CDF), then
e2=(beb)2
“double tag”
e1=2beb(1-beb)
“single tag”
e0=(1-beb)2
“no tag”
BR(tWb)/BR(tWq) >0.62 at 95% C.L.
R(eb-elight)
Does top decays into something besides SM Wb?
 Like Xb, where X  qq (100%) or Yb, where Y  ln (100%)?
Estimate branching limits using ratio of top cross sections sll/slj
Br(t  Xb) <0.46 at 95% C.L.
Dmitri Denisov, ICHEP04, August 21 2004
Br(t  Yb) <0.47 at 95% C.L. (CDF)
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CDF
Is Top to Wb vertex SM? W Helicity
Test of V-A coupling in top decays: in SM W couples only to LH particles
This together with angular momentum conservation allows top to decay into LH
(negative helicity) or longitudinally-polarized (0 helicity) W bosons
In SM F-=0.30, F0 =0.70, F+ =0
Helicity of W manifests itself in
decay product kinematics
CDF (l+jets and di-lepton)
F0  0.27 00..35
21 ( stat )  0.17( syst )
DØ (l+jets, 160 pb-1)
F+ < 0.24 at 90% C.L.
topological
F+ < 0.24 at 90% C.L.
b tagging
Dmitri Denisov, ICHEP04, August 21 2004
No deviations from SM predictions
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CDF
Experimental Limits on Higgs Mass
Available experimental limits
direct searches at LEP
MH >114 GeV at 95% C.L.
precision EW fits
mH  114 69
45 GeV
mH  260GeV
LEP
at 95% C.L.
Light Higgs favored
Tevatron provides:
Precision mt and Mw measurements
Direct searches
 SM Higgs
 non-SM Higgs
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
SM Higgs Production and Decays at Tevatron
Production
Production cross section
 in the 1 pb range for gg  H
 in the 0.1 pb range for associated
vector boson production
Decays
Decays
 bb for MH < 130 GeV
 WW for MH > 130 GeV
Search strategy:
MH <130 GeV associated production and bb decay W(Z)H  ln(l) bb
Backgrounds: top, Wbb, Zbb…
MH >130 GeV gg H production with decay to WW
Backgrounds: electroweak WW production…
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
SM Higgs Search: WH  lnbb (MH<130 GeV)
DØ uses sample of W(en)+2 b tagged jets
 Require exactly 2 jets to suppress top
background
2.5 events expected and 2 events observed
s(WH)xBR(Hbb) < 12.4 pb at 95% C.L.
For MH =115 GeV
CDF uses e and 
channels
Requires at least 1 jet
b tagged
Future improvements
Extend b-tagging
acceptance, efficiency
Additional kinematic
variables
Better Mbb resolution
Add nnbb channel
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
SM Higgs Search: H  WW  lnln (MH >130 GeV)
H
Search strategy:
 2 high Pt leptons and missing Et
 WW comes from spin 0 Higgs:
leptons prefer to point in the same direction
n
W+
e
n
W-
e-
+
DØ Run II Preliminary
Higgs of
160 GeV
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Current Limits on SM Higgs Search
Both experiments set 95% C.L. on
SM Higgs cross section x Br
Limits already exceeding Run I results
DØ light (115 GeV) Higgs search limit
s(WH)xBR(Hbb) < 12.4 pb-1 at 95% C.L.
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Tevatron SM Higgs Search: Outlook
Ldt, fb-1
LEP
Updated in 2003 in the low Higgs
mass region
W(Z)Hln(nn,ll)bb to include
 better detector understanding
 optimization of analysis
Tevatron
Sensitivity in the mass region above LEP limit starts at ~2 fb-1
Meanwhile
 optimizing analysis techniques
 understanding detectors better
 searching for non-SM Higgs with higher production cross sections or
enhanced branching into modes with lower backgrounds
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Search for MSSM Higgs
MSSM predicts larger Higgs cross sections for
some values of parameter space then SM
Using NLO cross section calculations and
assuming no difference between A and h/H
DØ performs search for MSSM Higgs
 multi-jet high Et sample
3 or more jets b tagged
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Search for MSSM Higgs
CDF searches for pp  h / A  X
With A decaying into  pair
 ~8% branching at high tanb
 lower backgrounds then bb pairs
No excess seen over backgrounds
Dmitri Denisov, ICHEP04, August 21 2004
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CDF
Search for H++/H--
Predicted by some beyond SM models like Left-Right
Symmetric Models
If short lived:
 prominent signature – multiple high Pt leptons,
like sign di-lepton mass peak
 backgrounds: WZ, W+jets, conversions (e)
D0 (113 pb-1) M(HL) > 118 GeV () at 95% C.L.
CDF (240 pb-1) M(HL) > 136 GeV () at 95% C.L.
q
*/Z
q
H++
l
+
l
+
l
-
l
-
H--
If long lived (c > 3 m):
 two high ionization tracks
Background < 10-5
MH>134GeV
Dmitri Denisov, ICHEP04, August 21 2004
32
CDF
Tevatron Top and Higgs: Summary
Many excellent talks about top and Higgs studies at Tevatron are presented at ICHEP04
EW, Beyond SM, Heavy Quarks sessions
Top studies are actively progressing:
 updated stt, mt , limits on single top production
 studies of SM predictions and beyond SM models
 W helicity studies
 decay modes: Wq, WX, Xq...
 tt resonances,…
No deviations from SM observed (yet)
Higgs search is in progress:
 SM Higgs
 sensitivity (mH >114 GeV) starts at ~2 fb-1
 non-SM Higgs
 many different models tested
 already see reduction in allowed phase space (Run I, LEP)
Expect substantial improvements in top studies, Higgs hunting with
~0.5 fb-1 already on tapes
~8 fb-1 expected in Run II
Dmitri Denisov, ICHEP04, August 21 2004
33
CDF
Expected Run II Top Quark Studies Accuracy
Some measurement targets
to aim for in Run II
Measurement
Top Mass
Dmitri Denisov, ICHEP04, August 21 2004
Precision
2-3 GeV/c2
s(ttbar)
9%
s(ll)/s(l+j)
12%
B(tWb)
2.8%
B(Wlongitudinal)
5.5%
Vtb
13%
B(tc)
2.8 X 10-3
B(tZc)
1.3 X 10-2
34
CDF
Search for H  
In the SM Higgs   has Br~10-3
 search for SM Higgs decaying to
gamma pair is not practical at Tevatron
Many SM extensions allow enhanced
gamma pair decay rate largely due to
suppressed coupling to fermions
 Fermiphobic Higgs
 Topcolor Higgs
Search strategy:
Look for peaks in  mass spectrum for
high Pt isolated ’s
Dmitri Denisov, ICHEP04, August 21 2004
35
CDF
Experimental Challenges
Collecting data at energy frontier is nontrivial
Not new physics, just welding induced noise  resolved
Large particle fluxes  irradiation issues
Small bunch spacing and large number of
interactions per crossing
 event synhronization
 complex event topology
Unexpected…
CDF central tracking chamber  aging resolved
Dmitri Denisov, ICHEP04, August 21 2004
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Resonances in tt system?
CDF
No resonance production in tt system is expected in SM
Some models predict tt bound states, example: topcolor-assisted technicolor
 predicts leptophobic Z’ with strong 3rd generation coupling
Experimental check: search for bumps in tt effective mass spectrum
DØ, 125 pb-1
Total
Top
MX > 560 GeV
Background
Dmitri Denisov, ICHEP04, August 21 2004
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