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XXXVI International Meeting on
Fundamental Physics
Physics at the Tevatron
From IMFP2006 → IMFP2008
Rick Field
University of Florida
(for the CDF & D0 Collaborations)
2nd Lecture
Bosons, Top, and Higgs
Palacio de Jabalquinto, Baeza, Spain
CDF Run 2
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 1
February 5, 2008
Tevatron Performance
The data collected since IMFP 2006 more than doubled
the total data collected in Run 2!
IMFP 2008
IMFP 2006 ~3.3 fb-1 delivered ~1.6 fb-1
~1.5 fb-1 delivered ~2.8 fb-1 recorded
~1.2 fb-1 recorded Integrated Luminosity per Year
23 tt-pairs/month!
Luminosity Records (IMFP 2006): Luminosity records (IMFP 2008):
Highest Initial Inst. Lum: ~1.8×1032 cm-2s-1 Highest Initial Inst. Lum: ~2.92×1032 cm-2s-1
Integrated luminosity/week: 25 pb-1 Integrated luminosity/week: 45 pb-1
Integrated luminosity/month: 92 pb-1 Integrated luminosity/month: 165 pb-1
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 2
February 5, 2008
Many New Tevatron Results!
Some of the CDF Results since IMFP2006
Observation of Bs-mixing: Δms = 17.77 ± 0.10 (stat) ± 0.07(sys).
Observation of new baryon states: Sb and Xb.
Observation of new charmless: B→hh states.
Evidence for Do-Dobar mixing .
Precision W mass measurement: Mw = 80.413 GeV (±48 MeV).
I cannot measurement: Mtop all the
Precision Top masspossibility cover = 170.5 (±2.2) GeV.
great physics results from the
W-width measurement: 2.032 (±0.071) GeV.
Tevatron since IMFP pb.
WZ discovery (6-sigma): s = 5.0 (±1.7)2006!
I (3-sigma).
ZZ evidence will show a few of the results!
Single Top evidence (3-sigma) with 1.5 fb-1: s = 3.0 (±1.2) pb.
|Vtb|= 1.02 ± 0.18 (exp) ± 0.07 (th).
Significant exclusions/reach on many BSM models.
Constant improvement in Higgs Sensitivity.
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 3
February 5, 2008
Z-boson Cross Section (CDF)
IMFP2006
QCD
Drell-Yan
Impressive agreement between experiment
and NNLO theory (Stirling, van Neerven)!
CDF (pb) NNLO (pb)
s(Z→e+e-) 254.93.3(stat)4.6(sys)15.2(lum) 252.35.0
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 4
February 5, 2008
Z-boson Cross Section (CDF)
IMFP2006
Impressive agreement between experiment and NNLO theory
(Stirling, van Neerven)!
CDF (pb) NNLO (pb)
s(Z→m+m-) 261.22.7(stat)6.9(sys)15.1(lum) 252.35.0
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 5
February 5, 2008
Z-Boson Rapidity Distribution
since IMFP2006
Measure ds/dy for Z→e+e-. Use electrons
in the central (C) and plug (P) calorimeter.
Parton momentum fractions x1 and x2 determine the Z boson
rapidity, yZ.
Production measurement in high yZ region probes high x
region of PDF’s.
Plug-plug electrons, ZPP, are used to probe the high x region!
1.1fb-1 91,362 events 66 < MZ < 116 GeV Plug-Plug
electrons!
CDF ZCC ZCP ZPP
Events 28,097 46,676 16,589
Zcc Zcp Zpp
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 6
February 5, 2008
Z-Boson Rapidity Distribution
since IMFP2006
CDF measured ds/dy for Z/g*
compared with an NL0 calculation
using CTEQ6.1M PDF.
The NLO theory is scaled to the
measured s(Z)!
No PDF or luminosity uncertainties
included.
NLO NNL0 MRST PDF
NLL0 + + CTEQ6.1 PDF NLO + MRST PDF
CDF (pb) NNLO (pb)
s(Z→e+e-) 263.3±0.9(stat)±3.8(sys) 252.35.0
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 7
February 5, 2008
The Z→tt Cross Section (CDF)
Taus are difficult to reconstruct at hadron colliders Signal
cone
• Exploit event topology to suppress backgrounds (QCD & W+jet).
• Measurement of cross section important for Higgs and SUSY analyses.
CDF strategy of hadronic τ reconstruction:
• Study charged tracks define signal and isolation cone (isolation = require no
tracks in isolation cone).
• Use hadronic calorimeter clusters (to suppress electron background).
• π0 detected by the CES detector and required to be in the signal cone.
CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of
EM calorimeter. Isolation
cone
Channel for Z→ττ: electron + isolated track
• One t decays to an electron: τ→e+X (ET(e) > 10 GeV) .
• One t decays to hadrons: τ → h+X (pT > 15GeV/c).
Remove Drell-Yan e+e- and apply event topology cuts for non-Z
background.
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 8
February 5, 2008
The Z→tt Cross Section (CDF)
CDF Z→ττ (350 pb-1): 316 Z→ττ candidates. IMFP2006
Novel method for background estimation: main contribution QCD.
τ identification efficiency ~60% with uncertainty about 3%!
1 and 3 tracks,
same sign,
opposite sign
opposite sign
CDF (pb) NNLO (pb)
s(Z→t+t-) 264 ± 23 (stat) ± 14 (sys) ± 15 (lum)
26520(stat)21(sys)15(lum) 252.35.0
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 9
February 5, 2008
Higgs → tt Search (CDF)
IMFP2006 140 GeV
Higgs Signal!
Data mass distribution agrees with SM expectation:
• MH > 120 GeV: 8.4±0.9 expected, 11 observed.
Fit mass distribution for Higgs Signal (MSSM scenario):
• Exclude 140 GeV Higgs at 95% C.L.
• Upper limit on cross section times branching ratio.
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 10
February 5, 2008
Higgs → tt Search (CDF)
since IMFP2006
No Significant Excess of events above SM background is observed!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 11
February 5, 2008
W-boson Cross Section (CDF)
Extend electron coverage to the forward
region (1.2 < |h| < 2.8)! IMFP2006
48,144 W candidates ~4.5% background
overall efficiency of signal ~7%
CDF NNLO
s(W)/s(Z) 10.920.15(stat)0.14(sys) 10.690.08
s(W) L CDF (pb) NNLO(pb)
Central 72 pb-1 277510(stat)53(sys)167(lum) 268754
electrons
Forward 223 pb-1 281513(stat)94(sys)169(lum) 268754
electrons
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 12
February 5, 2008
W-Boson Mass Measurement
since IMFP2006
The Challenge:
Do not know neutrino pz.
No full mass reconstruction possible.
Extract from a template fit to PT, MT, and
Missing ET.
Transverse mass:
MW = 80413 ± 48 MeV/c2
Single most precise measurement to date!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 13
February 5, 2008
W-Boson Width Measurement
since IMFP2006
Model transverse mass distribution
over range 50-200 GeV.
Normalize 50-90 GeV and fit for the width in the high
MT region 90-200 GeV.
The tail region is sensitive to the width of the Breit
Wigner line-shape.
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 14
February 5, 2008
W Production Charge Asymmetry
There are more u-quarks than d-quarks at high x in
xG(x,Q2)
the proton and hence the W+ (W-) is boosted in the Q2 = 100 GeV2
direction of the incoming proton (antiproton).
MRST2004NLO
Measuring the W± asymmetry constrains the PDF’s!
u
e+
u d
W+ d
p d u
p x
u u 10-3 10-2 10-1 1
ne
W- W+
ds / dyW ds / dyW
A( yW )
ds / dyW ds / dyW
antiproton proton
y
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 15
February 5, 2008
W Production Charge Asymmetry
Since the longitudinal momentum of the neutrino,
pL(n), is not known the W rapidity cannot be
reconstructed.
since IMFP2006
So previously one looked at the the electron
charge asymmetry.
The V-A structure of the W+ (W-) decay favors a
backward e+ (forward e-) which “dilutes” the W
charge asymmetry!
New CDF measurement performed in W→en
channel.
pL(n) is determined by constraining MW = 80.4
GeV leaving two possible yW solutions. Each
solution receives a probability weight according
to the V-A decay structure and the W cross-
section, s(yW).
The process is iterated since s(yW) depends on the
asymmetry.
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 16
February 5, 2008
W + g Cross Sections (CDF)
IMFP2006
ET(g) > 7 GeV
R(lg) > 0.7
CDF (pb) NLO (pb)
s(W+g)*BR(W->ln) 19.71.7(stat)2.0(sys)1.1(lum) 19.31.4
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 17
February 5, 2008
W + g Cross Sections (CDF)
since IMFP2006
ET(g) > 7 GeV
R(lg) > 0.7
CDF (pb) NLO (pb)
s(W+g)*BR(W->ln) 19.71.7(stat)2.0(sys)1.1(lum)
18.03±0.65(stat)±2.55(sys) ±1.05(lum) 19.31.4
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 18
February 5, 2008
Z + g Cross Sections (CDF)
IMFP2006
Note: s(Wg)/s(Zg) ≈ 4
while s(W)/s(Z) ≈ 11
ET(g) > 7 GeV
R(lg) > 0.7
CDF (pb) NLO (pb)
s(Z+g)*BR(Z->ll) 5.30.6(stat)0.3(sys)0.3(lum) 5.40.3
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 19
February 5, 2008
Z + g Cross Sections (CDF)
since IMFP2006
390 events
ET(g) > 7 GeV
R(lg) > 0.7
Meeg > 40 GeV/c2
CDF (pb) NLO (pb)
s(Z+g)*BR(Z->ee) 4.90.3(stat)0.3(sys)0.3(lum) 4.70.4
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 20
February 5, 2008
The W+W Cross-Section
IMFP2006
Campbell & Ellis 1999
pb-1 CDF (pb) NLO (pb)
s(WW) CDF 184 14.6+5.8(stat)-5.1(stat)1.8(sys)0.9(lum) 12.40.8
s(WW) DØ 240 13.8+4.3(stat)-3.8(stat)1.2(sys)0.9(lum) 12.40.8
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 21
February 5, 2008
The W+W Cross-Section (CDF)
IMFP2006
WW→dileptons + MET
Two leptons pT > 20 GeV/c.
Z veto.
MET > 20 GeV.
Zero jets with ET>15 GeV
and |h|<2.5.
We are beginning to study the details of 95 events with
Observe
37.2
Di-Boson production at the Tevatron! background!
L CDF (pb) NLO (pb)
s(WW) 825 pb-1 13.72.3(stat)1.6(sys)1.2(lum) 12.40.8
Missing ET! Lepton-Pair Mass! ET Sum!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 22
February 5, 2008
WW+WZ Cross-Section since IMFP2006
NLO Theory
σWW × Br(W→ln, W→jj) = 12.4 pb × 0.146 = 1.81 pb
σWZ × Br(W→ln, Z→jj) = 3.96 pb × 0.07 = 0.28 pb
CDF (pb) NLO (pb)
s(WW+WZ)×BR(lvjj) 1.47 ± 0.77(stat) ± 0.38(sys) 2.1 ± 0.2 pb
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 23
February 5, 2008
The Z+W, Z+Z Cross Sections
IMFP2006 W+Z → trileptons + MET
Observe 2 events with a
background of 0.9±0.2!
Upper Limits
W+Z, Z+Z Limit (pb) NLO (pb)
CDF (194 pb-1) sum < 15.2 (95% CL) 5.00.4
DØ (300 pb-1) W+Z < 13.3 (95% CL) 3.70.1
CDF (825 pb-1) W+Z < 6.34 (95% CL) 3.70.1
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 24
February 5, 2008
The W+Z Cross Section since IMFP2006
Strategy
Search for events with 3 leptons and missing
energy.
Small cross-section but very clean signal.
Anomalous cross-section sensitive to non SM
contributions.
3.0 σ significance!
L CDF (pb) NLO (pb)
s(W+Z) 1.9 fb-1 4.3±1.3(stat) ±0.2(sys) ±0.3(lum) 3.70.3
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 25
February 5, 2008
The Z+Z Cross Section since IMFP2006
Strategy:
Search for events with either 4 leptons or
2 leptons and significant missing ET.
Calculate a Prob(WW) or Prob(ZZ) based on event
kinematics and LO cross section.
Construct a likelihood ratio.
Fit to extract the llnn signal.
ZZ decaying into leptons +
ZZ decaying into 2 4 leptons MET
3.0 σ significance!
L CDF (pb) NLO (pb)
s(Z+Z) 1.9 fb-1 0.75+0.71-0.54 1.4±0.1
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 26
February 5, 2008
Higgs → W+W
We are within a factor of two of since IMFP2006
the standard model
Higgs (160 GeV) → WW!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 27
February 5, 2008
Heavy Quark Production at the Tevatron
with 1 fb-1 Total inelastic stot ~ 100 mb which is
~1.4 x 1014 103-104 larger than the cross section for
D-meson or a B-meson.
However there are lots of heavy quark
events in 1 fb-1!
~1 x 1011
Want to study the production of
charmed mesons and baryons: D+, D0,
Ds , lc , cc , Xc, etc.
~6 x 106
Want to studey the production of
~6 x 105
B-mesons and baryons: Bu , Bd , Bs , Bc ,
lb , Xb, etc.
~14,000
~5,000 Two Heavy Quark Triggers at CDF:
• For semileptonic decays we trigger on
m and e.
• For hadronic decays we trigger on one
or more displaced tracks (i.e. large
impact parameter).
CDF-SVT
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 28
February 5, 2008
B-Baryon Observations (CDF)
since IMFP2006
The Tevatron is excellent at
Xb
producing particles containing b
and c quarks
(Bu, Bd, Bs, Bc, Sb, Xb,b)
Sb
bc
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 29
February 5, 2008
Top Decay Channels
mt>mW+mb so dominant decay tWb.
The top decays before it hadronizes.
B(W qq) ~ 67%.
B(W ln) ~ 11% l = e, m, t.
BR background
dilepton ~5% low
lepton + jets ~30% moderate
all hadronic ~65% high
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 30
February 5, 2008
Dilepton Channel (CDF)
Selection:
2 leptons ET > 20 GeV with opposite sign. Backgrounds:
since IMFP2006
•
• >=2 jets ET > 15 GeV. • Physics: Drell-Yan, WW/WZ/ZZ,
Z tt
• Missing ET > 25 GeV (and away from any jet).
• Instrumental: fake lepton
• HT=pTlep+ETjet+MET > 200 GeV.
• Z rejection.
IMFP2006
84 events
65 events
20 events
background
s(tt) = 8.3 ± 1.05 (stat) 1.0 (syst) + 0.5 (lumi) pb
s(tt) = 6.16± 1.5 (stat) ± ± 0.72 (syst) + 0.37 (lumi) pb
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 31
February 5, 2008
Lepton+Jets Channel (CDF)
b-Tagging
Require b-jet to be tagged for
discrimination.
Tagging efficiency for b jets~50%
for c jets~10%
1 b tag for light q jets < 0.1%
IMFP2006
2 b tags
~70 events
HT>200GeV ~180 events
~150 events ~45 events
Small
background!
s(tt) = 8.8 ±0.5 (stat) ±0.8 (sys) ± 0.5 (lum)pb 1.1
s(tt) = 8.2 ± 0.6 (stat) ± 1.1 (syst)± 0.5 (lum) pb 1.2 (stat)2.0 (syst)pb
0.8 1.2 (sys) pb s (tt ) 8.8 1.3
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 32
February 5, 2008
Tevatron Top-Pair Cross Section
since IMFP2006
CDF Run 2 Preliminary
Theory
s (tt ) 6.70.9 pb
0.7
Bonciani et al., Nucl. Phys. B529, 424 (1998)
Kidonakis and Vogt, Phys. Rev. D68, 114014 (2003)
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 33
February 5, 2008
Top Quark Mass
since IMFP2006
Dilepton Channel
Leptons+Jets Channel
Mt=170.4 ± 3.1(stat) ± 3.0(sys)GeV/c2
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 34
February 5, 2008
Top Cross-Section vs Mass
Tevatron Summer 2005 CDF Winter 2006
CDF combined
Cacciari, Mangano, et al., hep-ph/0303085
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 35
February 5, 2008
Constraining the Higgs Mass
Top quark mass is a fundamental
parameter of SM.
Radiative corrections to SM Tevatron Run I + LEP2
predictions dominated by top Summer 05
mass.
Top mass together with W mass
places a constraint on Higgs
mass!
114 GeV Higgs very interesting for
the Tevatron!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 36
February 5, 2008
Other Sources of Top Quarks
Strongly Produced tt Pairs
Dominant production mode
sNLO+NLL = 6.7 1.2 pb g q ~85% t
Relatively clean signature ~15%
Discovery in 1995 g q t
ElectroWeak Production: Single Top
Larger background
Smaller cross section s ≈ 2 pb
Not yet observed!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 38
February 5, 2008
Single Top Production
s-channel t-channel tW associated production
q q W * tb qb q ' t bg tW
Combine
(mtop=175 GeV/c2) s-channel t-channel Associated tW
(s+t)
Tevatron sNLO 0.88 0.11 pb 1.98 0.25 pb ~ 0.1 pb
LHC sNLO 10.6 1.1 pb 247 25 pb 62+17 -4 pb
Run I CDF < 18 pb < 13 pb < 14 pb
95% C.L.
D0 < 17 pb < 22 pb
B.W. Harris et al.:Phys.Rev.D66,054024 T.Tait: hep-ph/9909352
Z.Sullivan Phys.Rev.D70:114012 Belyaev,Boos: hep-ph/0003260
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 39
February 5, 2008
Single Top at the Tevatron
IMFP2006 95% C.L. limits on single top cross-section
Channel CDF (696 pb-1) DØ (370 pb-1)
Combined 3.4 pb (2.9 pb)
s-channel 3.2 pb (0.9 pb) 5.0 pb
t-channel 3.1 pb (2 pb) 4.4 pb
The current CDF and DØ analyses not only provide drastically improved
limits on the single top cross-section, but set all necessary tools and
methods toward a possible discovery with a larger data sample!
Both collaborations are aggressively working on improving the results!
Theory!
Single Top Discovery is Possible in Run 2 !!!!
- R. Field (IMFP2006)
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 40
February 5, 2008
Single Top Production
since IMFP2006
Single Top
Signal!
DØ Combination
3.6s!
3.4s!
Expected sensitivity: 2.1s
ss+t= 4.9 ±1.4 pb
ss= 1.0, st =4.0 pb First direct measurement of Vtb
0.68 <|Vtb|< 1 @ 95%CL or
PRL 98 18102 (2007) |Vtb| = 1.3 ± 0.2
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 41
February 5, 2008
Single Top Production since IMFP2006
3.1s!
ss+t= 2.7 ± 1.2 pb ss+t= 3.0 ± 1.2 pb
ss= 1.1, st =1.3 pb ss= 1.1, st =1.9 pb
Expected sensitivity: 2.9s Expected sensitivity: 3.0s
Observed significance: 2.7s
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 42
February 5, 2008
Measurement of |Vtb| (CDF)
Using the Matrix Element cross section CDF Run II Preliminary L=1.5 fb-1
measurement, CDF determines |Vtb|
assuming |Vtb| >> |Vts|, |Vtd|!
s-channel
t-channel
|Vtb|= 1.02 ± 0.18 (exp) ± 0.07(thy)
DØ |Vtb|>0.68, |Vtb| = 1.3 ±0.2 Z. Sullivan, Phys.Rev. D70 (2004) 114012
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 43
February 5, 2008
Single Top Candidate Event
t-channel single top production has a t-channel
kinematic peculiarity. single top!
EPD > 0.9
Distinct asymmetry in lepton charge Q
times the pseudo-rapidity of the untagged
jet! Central Electron Candidate
Charge: -1, Eta=-0.72 MET=41.6 GeV
u d
Jet1: Et=46.7 GeV Eta=-0.6 b-tag=1
Jet2: Et=16.6 GeV Eta=-2.9 b-tag=0
Q×h = 2.9 (t-channel signature)
EPD=0.95
CDF Run: 211883, Event: 1911511
Jet1
Lepton
Jet2
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 44
February 5, 2008
Single Top at the Tevatron
since IMFP2006
Single top cross-section measurements!
Channel Theory CDF (1.5 fb-1) DØ (0.9 fb-1)
Combined 2.9 pb 3.0 ± 1.2 pb 4.9 ± 1.4 pb
s-channel 0.9 pb ≈ 1.1 pb ≈ 1.0 pb
t-channel 2.0 pb ≈ 1.9 pb ≈ 4.0 pb
Single top has (almost) been seen at the Tevatron at the
expected rate!
If you think 3.5s is enough to claim discovery?
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 45
February 5, 2008
Top-AntiTop Resonances
CDF Run 1
Excess is
reduced!
Phys.Rev.Lett. 85, 2062 (2000)
CDF observed an intriguing excess of events with top-antitop invariant mass
around 500 GeV!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 46
February 5, 2008
Top-AntiTop Resonances
The excess has disappeared!
since IMFP2006
Excess is
gone!
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 47
February 5, 2008
Tevatron Measurements
Jets
b-quarks
We are getting very close to
W
the Higgs and/or new physics!
Z
W+g
Single top
Z+g
W+W
tt
W+Z
Z+Z
IMFP2008 - Day 2 Rick Field – Florida/CDF/CMS Page 48
February 5, 2008
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